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NPIW ZEALAND GEO L()«I(5AL SURVEY 

(J. M. BELL, Director.) 



o 



BULLETIN No. 9 (New Series] 



THE GEOLOGY 



OK THK 



WHATATUTr SUJ^DiVJSION, 

RAUKIJMAKA DI \'i SION. POXEKTY BAY. 



.)AMi:s iii:nkv adams. 



ISSUKK INDKl; THK ALTUOIil TV OK THK HON K. McKKN/IK MIMS'IKK OK MINK- 




NEW ZEALAND. 
PA' AUTHOHITY : JOHN MACKAY, (iOVERNMEN T PRINTER, WELLINGTON. 

1910 



LETTER OF TKANSMITTAL. 



(iE()i,o(iicAL Survey Office, 

Wellington. 6tli -Inne, 1910. 

SlK,— 

J lia\(' the honour to >ul)niit herewith Bulletin No. !) ot tlic 
New Ze.iliinil ( leolo^ical Survey. 

It contains the results of the work conducted liy Mr. -1. H. .-Vdanis, 
Assistant Gcoloj^ist, in the Whatatutu Suhdivision of the Kaukuinara 
Division, I'oxrrty Hay, duiin.n' the field seasons of 1008-9. 

riic hullctin is accompanied hy live niaps, and is illustrated liy 
three plates. 

1 have the honour to he, 
Sir, 
Your obedient servant^ 

.1. M. 15ELL, 
Director, N./. (leological Survey. 
Hon. K. McKen/ie, 

Minister of Mines, 

Wellington. 



CONTENTS. 



Letter i>f Thansmittai 



Page 
iii 



ChAI'TEK I. — (iEXERAl. INFORMATION. 



Introduction 

Area described in tlii^ lieport 

Previous Geoloj^ical Investigations 

renditions of Oolo^'ical Work, and Method 

of conducting F'ield Operations . . 
Surface Boring at Waitangi Hill 
Soil and Agriculture 
Timber 



Pajie 
I 



-Means of Coinniunication 

History of the Attempts to establ 

troleum Industry 
Plusical (Jeographv 
Outline of (ieology 

(Jcological Sequence 

(ieological History 
Literature 



sh a Pe 



Page 
4 



8 

9 

9 

10 

10 



(.Jlassitication 

The VVhatatutu Scries 

I. The Lower Whatatutu Beds , 

II. The I'pper Whatatutu Beds 
Palaeontology 

Structure 

Introduction 



Chapter H. — General Geology. 

12 Structure — continued. 
12 (ieneral Structure 

12 Detailed Structure 

1') The Waipaoa Series 

21 Loosely consolidated 

.. 2:5 Debris 

. . 23 Faults . . 



mconsolidati 



24 
25 
32 

32 
32 



Chapter HI. — Kt< 

Petroleum . . . . ..'.}'> 

Origin of Petroleum . . . . 35 

(1.) Theory of Inurganic Origin 35 

(2.) Theory of (Jrganic Origin . . 35 

Petroleum-indications . . . . 3f) 

(1.) Oil .. .. .. 3ti 

Occurrences within the Subdivision 3ii 
Occurrences without the Subdivi- 
sion . . . . . . 37 

Analyses of the Oil . . 37 

(2.) Gas ".. .. ..37 

General Occurrence 39 

Occurrences within and near the 

Sulxlivision . . . . . . 39 



xoMic Geology. 




Petroleum — continued. 




Probable Oil Zone 


. 40 


Sites for Boreholes 


. 40 


Material for Macadaniisiti.' Pinposes 


. 42 


( 'onglomerate . . 


. 43 


Burnt Papa or Claystone 


. 43 


Mat<Tials for Cement-making, &e. .. 


. 44 


Limestone 


. 44 


Clays. . . . . 


. 44 


Gold" .. 


. 45 


Coal 


. 41) 


Mineral Spring 


. 41) 



L I ST OF I LLIJST KATl ON S 



Plat*' I. Waitangi Oil Bore on Opening-ilay 

Waipaoa Station, looking West across the .Mangatu Fein Country 
Plate II. Looking up Waipaoa Hiver from Mr. H. Tiffen's (Jate: Tawhiti in Di.stance 
Plat.- III. .Main Petroleum Sjiriug. Waitansi Hill 

Flood Plain of Waingariimia Stream 



Facing page 



8 
18 
38 



LIST OV M A P S 



1. Map of New Zealand, showing Land Districts and Divisions 

2. Map of Raukumara Division, showing Survey Districts and Area geologically surveyed . . 

3. Geological .Map of Mangatu Survey District, with (Jeologioal Section from West to Ea.st . . 

4. Geological Map of Waingaromia Survey District, with Geological Section from West to East 

5. Map showing Site of Petroleum Indications in the Waingaromia Survey District 



Facing page 
vi 
vi 
12 
32 
3fi 




•ooo.^oa. ji« 



By Authority : John hitkukay^ Govemmtni Pnnttr, 




Jy AwtkoHtu : Johm tlaokai/, QoiMmm^ttt Printer. 



/00.6 fo.s7e 



BULLETIN No. 9 (NEW SERIES) 



THE GEOLOGY 



OP THE 



WHATATUTU SUBDIVISION, 

RAUKUMARA DIVISION. 



CHAPTER I. 



Page 






Page 


1 


Means of Commimication 




. 4 


2 


History of tlie Attempts 


to establish 


a 


2 


Petroleum Industry 




. 5 




Physical (ieography . . 




8 


1 2 


Outline of (Jeology — 






2 


Geological Sequence 




. !t 


4 


Geological History 




. 10 


4 


Literature 




. 10 



GENERAL INFORMATION. 



Introduction 

Area described in this Report 
Pi-evious Gooloi;ical Investigations 
Conditions of (Jeological work, and 
Method of conducting Field Operations 
Surface Boriiis^ at VV^aitangi Hill 
Soil and Agriculture 
Timber 

Introduction. 

Thk Raukumara Division lies between latitudes 37° 30' and 39° S., on the eastern side of the 
North Island of New Zealand. 

This division comprises the northern portion of the Hawke's Bay Land District. It is 
hounded to the north and east by the waters of the Pacific Ocean. To the westward its 
boundary is formed by an irregular line extending in a general south-westerly direction from 
Potiki Rua, a point on the coast-line three miles and a half east of Cape Runaway, to the 
Te Hoe Stream, a loft branch of the Mohaka River. This line has its course along a portion 
of the crest of the Raukumara Range, follows the bed of the Motu River for some miles, skirts 
the northern and western shores of Lake Waikaremoana, and finally passes down the Te Hoe 
■Stream as far as the 39th parallel of latitude. To the southward it is bounded by that portion 
of the 39th parallel of latitude which lies between the Te Hoe Stream and the eastern sea-coast 
of the North Island of New Zealand. 

The Raukumara Division is essentially an agricultural and pastoral district. All its more 
accessible portions are at the present time being worked for these purposes with very satisfactory 
results. By far the greater portion so far settled is devoted to the pasturage of sheep. Cattle- 
riiisiiig. though <artied on to a vary apprecial)le oxteut, is. of secondary moment. Dairy- 
farming is growing in impoitiincc, and a«v<;tu4 butter-factories Uj^vc beeu established. 

1— Wnalatulu. 



Many thousands of acres of land with in the Raukumara Division are still covered with 
native bush, especially in the northern portions, where means of communication with esta- 
blished settlements are not good. 

The surface indications of oil which occur in various localities throughout the Raukumara 
Division are suggestive of the existence of hidden mineral wealth. Many thousands of pounds 
sterling have already been expended in boring for oil. without,- however, any return to the 
investors. A propos of this point, it may be stated that these past operations were carried 
on without any knowledge of the structure of the underlying rock-masses, and the geological 
examinations forming the subject of the present report were imdertaken with a view to giving 
direction to future boring operations. 

Area described in this Report. 

The first portion of the Raukumara Division to be geologically examined in detail com- 
prises the survey districts of Mangatu and Waingaromia, which represent what is called the 
Whatatutu Subdivision. This area occupies an approximately central position in the division, 
and has the form of a rectangle 25 miles from east to west by \2\ miles from north to south. 
Its superficial area is thus 312-5 square miles. Its southern boundary is 16 miles north of the 
town of Gisborne, and its eastern boundary 10 miles west of the village of Buckley (Tolaga 
Bay). The Whatatutu Subdivision contains the most prominent petroleum-seepage so far 
discovered in this part of New Zealand — namely, the oil-springs at Waitangi Hill. 

Previous Geological Investigations. 

In March and April, 1874, a geological examination of the country lying between Poverty 
Bay and the East Cape was made by the late Sir James Hector. In his report relating to 
this district he describes the geology of the vicinity of the oil-springs at Waitangi Hill. 

In May, 1874, Mr. Alexander McKay collected fossils from the beds exposed in the Waipaoa 
River and from the area in the vicinity of Waitangi Hill. 

In 1901 the same geologist examined the area covered by the Whatatutu Subdivision, 
and a considerable portion of the adjacent country. In his report on these investigations 
he suggests as favourable localities for boring for oil the Mangatu Valley between Mangamaia 
and Te Hua homesteads, and the Waikohu Valley west of Poututu accommodation-house. 

Conditions of Geological Work, and Method of conducting Field Operations. 

The general conditions within the Whatatutu Subdivision are not so favourable for 
geological investigation as might be expected from the topographical relief of the area. The 
rock formations are for the most part subject to rapid surface-decomposition, owing to which 
the crests and slopes of the ridges and spurs have become covered with a thick mantle of dis- 
integrated rock. The beds of the main streams and of their tributaries afford the best outcrops 
for aiding the geologist in the mapping of the varied strata. Faces exposed by land-slips on 
the slopes of spurs and ridges occur sparingly, but give useful information. 

In carrying out the field-work every effort has been exerted to make the examination 
as thorough as possible. The accurate location of the geological and topographical features 
necessitated a great amount of traversing. Maps drawn on a scale of 20 chains to an inch, 
from information obtained from the Lands and Survey Department, were used as a basis 
for plotting, and to these maps much topographical information has been added. 

Surface Boring at Waitangi Hill. 
With the intention of obtaining information as to the rock formation immediately below 
the surface soil in the vicinity of a site for boring at Waitangi Hill, recommended by the 
Geological Siirvey, five bores were sunk to a depth of about 60 ft. The following table gives the 
" log " of each bore : — 




I'— 



Wbatatutu. 



The borehole which is at present being sunk by the Gisborne Oil Company is exactly 
on the site of No. 1 bore ; Nos. 2, 3, and 4 are within a radius of 9 chains from No. 1 ; No. 5 
is distant 21^ chains from No. 1 in a north-western direction. 

A comparison of the material obtained in these bores shows that in the first four there 
is a marked similarity. It would seem that at about 40 ft. decomposed claystone or argillaceous 
sandstone occurs. It may be worthy of note that in the first four boreholes a small flow of 
water was met with at about 10 ft., while in No. 5 the hole was dry to 48 ft. All the bores 
were sunk vertically. 

Soil akd Agriculture. *^ 

The ^^'^latatutu Subdivision, from its mild relief ; its well-distributed watercourses, 
flanked for the most part by terrace flats ; its abundance of fresh-water springs ; its native 
bush supplying timber for building and fencing purposes ; its general geological formation, 
consisting of claystones, fossiliferous sandstones, and limestones, has many natui'al advantages 
as an area for carrying on sheep-farming and agriculture. That this combination of natural 
gifts has been to some extent recognised may be judged from the fact that these .312| square 
miles, or 200,000 acres of laud, wintered, during each of the years 1907 and 1908, some 280,000 
sheep and lambs — that is, over IJ sheep per acre. When it is taken into consideration that 
many of the lots within the area have been comparatively recently settled, so that large 
portions of them are still covered with native bush or have been but recently cleared, one 
cannot but anticipate a very prosperous future for the sheep-farming industry in this district. 

The extensive high- and low-level terraces which flank that portion of the Waipaoa River 
between the village of Whatatutu and the southern limits of the subdivision are well adapted 
for agricultural purposes, and will probably in time be solely devoted to these purposes. 

Timber. 
The most important timber-trees of the district, placed in order of their economic im- 
portance, are. — 

Totara {Podocarpus total a), 

Kahikatea, or white-pine (Podocarpus dacrydioides), 
Matai, or black-pine {Podocarpus spicatus), 
Towai, kamahi, or black-birch (W einmannia racemosa), 
Rimu {Dacrydium cupressinum), 
Kowhai {Sophora tetraptera) 
Rewarewa (Knightia excelsa), 
Pukatea (Laurelia novce-zealandicB), 
Rata {Metrosideros robusta). 
The totara, kahikatea, matai, and pukatea do not extend beyond 2,000 ft. above sea- 
level ; the remainder, however, are found growing at elevations up to 2.500 ft. and .3,000 ft. 

Totara, kahikatea, matai, and towai are the timbers used in general for fencing-posts, 
while battens for the fences are made from nearly all the timbers mentioned. In manv parts 
of the subdivision timber has become scarce, since the area is essentially a sheep-farming 
one, and in the process of clearing the land the necessary burning which follows the bush-felhng 
often destroys such reserves as mav have been left for the sake of the timber contained. 

Means of Communicatiojt. 

As yet there is no railroad within the "VMiatatutu Subdivision, but the railway from Gisborne 
westwards towards Motu passes through the tillage of Fulia, which is situated about two miles 
south of the median point of the southern boundary. 

The area is fairly well supphed with formed roads and tracks, but none of them is mac- 
adamised. Consequently, in summer the roads become exceedingly dusty, whilst in winter the 
majority become quagmires along which vehicular progress is difficult and sometimes im- 
possible- 



Postal communication is fairly well developed. Wlatatutu, the only village witkin 
the subdivision, has a post-office and telephone biu'eau, and acts as a centre of communication 
for a large portion of the area. In addition, there are offices for the receipt and forwarding 
of letters and small parcels at Iwiroa, Wheturau, Kanakanae, ana Arakihi. 

Almost every homestead is connected by private telephone to the bureau .at Whatatutu, 
or to the bureaux at the villages of Puha, Te Karaka, Waimata, and Hauiti, situated but short 
distances outside the boundaries of the subdivision. 

History of the Attempts to establish a Petroleum Industry. 
In the year 1874 Waitangi Hill became the scene of active prospecting operations for 
petroleum. To many of those who first commenced work near the ])rominent oil-seepages 
occuning there it seemed necessary only to dig a pit of shallow depth to obtain an abundant 
supply of oil. That their expectations were not realised is only too well known, and the 
reported yield of 8 to 10 gallons per diem from one of these pits was probably the maximum 
obtained. 

In the vicinity of the main spring a shaft, closely timbered, was sunk to a depth of 100 ft., 
but, owing to the swelling nature of the ground and to the large volume of gas given oft", the 
sinking had to be discontinued. From the bottom, however, a borehole was sunk to a further 
depth of 110 ft., making a total depth of 210 ft. below the surface. These operations had also 
to be discontinued owing to the presence of the gas causing a shower of mud and water every 
time the rods were removed. 

In 1880 the South Pacific Petroleum Company commenced operations. In all, nine wells 
were drilled by this company — six at or in the immediate vicinity of the main oil-spring, two at a 
small oil-seepage 35 chains south of the former sites, and the last, known as the South Pacific 
borehole, a mile and a quarter south of the main oil-spring on the right or northern bank 
of the Waingaromia River. The first eight boreholes attained depths of from 100 ft. to a 
maximum of 500 ft. ; the ninth was considerably deeper. 

The South Pacific Borehole was commenced on the 11th December, 1884. Its initial 
diameter was 8 in. and final diameter 4^ in. In December, 1887, this well had reached a depth 
of 1,321 ft. It is reported that at this depth a " blow-out " of gas and oil took place. The 
gas and oil became ignited, and flared up to a height of some 20 ft., and continued to burn 
for over three hours. During this display the derrick was burned down, and all the machinery 
except the engine and boiler destroyed. A new derrick was erected, the tools recovered from 
the borehole, and drilling proceeded with for another few feet (reported as 15 ft.). If the 
alleged " blow-out " was genuine, the supply of oil must have been completely exhausted 
by this one spasmodic effort, for the hole was abandoned as " dry." The log of this borehole 
is appended : — 

Surface bouldere. 
Papa, or calcareous marl. 
Thin bands of sandstone showing gas and oil. 
Calcareous marl, brown shale, and " slate." 
Thin bands of sandstone with gas and oil. 
" Slate " and sandstone. 
Very hard grey sandstone. 
Gritty " slate " and thin bands of sandstone. 
" Sedimentary slate." 
Sandstone gixnng off gas and oil 
Soft sandstone and brown shale. 

Thin bands sandstone and conglomerate, giving gas and oil. 
Hard sandstone, with considerable gas. 
So far as can be gathered from this log. the rocks passed through belong to the upper portion 
of the Whatatutu Series. 



Surface 


to 85 ft. 


85 ft. 


„ 470 ft.. 


470 ft. 


,, 483 ft. 


483 ft. 


„ 780 ft. 


780 ft. 


„ 802 ft. 


802 ft. 


.. 912 ft. 


*)12ft. 


., 915 ft. 


915 ft. 


„ 1,105 ft. 


1,105 ft. 


„ 1,119 ft. 


1,119 ft. 


„ 1,140 ft. 


1.140 ft. 


„ 1,260 ft. 


1,260 ft. 


„ 1,307 ft. 


1,307 ft. 


„ 1,321 ft. 



6 

The choice of this site for a borehole was unfortunate, since it is situated ahnost in the 
trough of the Waingaromia syncline. On this account it is probable that a very great thick- 
ness of strata would have to be penetrated — much greater than would be the case if drilled 
on a denuded anticline — before reaching the supposed oil zone. Moreover the syncline is 
by no means a shallow one, and the conditions for the accumulation of oil in it are therefore 
unfavourable. 

Out of the authorised capital of £44,916 the South Pacific Petroleum Company, in January-, 
1888, had expended £22,000. 

On the 5th December, 1887, the Minerva Petroleum Company commenced a borehole on 
the left, or eastern, bank of the Waipaoa Eiver, at a point distant five miles south-west from 
the main oil-spring. The material passed through in the well is said to have been of a dis- 
tm'bed nature, but only concerning the last 50 ft. is definite information available. At 700 ft. 
gas was given off freely, and when caused to issue through a one-inch pipe burned with flame 
2 ft. in height. From 715 ft. to 747 ft. a red slaty shale yielding gas and oil was passed 
through, whilst from 747 ft. to 750 ft. a layer of puggy material was encountered, which finally 
caused the borehole to be abandoned. This borehole is located about one mile south of the 
crest of the Waitangi anticline ; but from the disturbed nature of the material penetrated 
it seems probable that it is on the line of the Waitangi fault. 

In Januarj', 1888, the Minerva Petroleum Company had expended £3,000 of its authorised 
capital of £5,000. 

From 1888 no drilling was carried on within or in the vicinity of the subdivision imtil 
the year 1903, when a well was sunk near the head of Totangi Stream, in the neighbourhood 
of the oil-seepages there. The well had an initial diameter of 4 in., which, owing to the diffi- 
culties experienced in the process of drilling, had continually to be reduced, until at 500 ft. 
it had become 2| in., and the well could not be sunk deeper. 

At the present time a well is being sunk at Waitangi Hill by the Gisborne Oil Company. 
The site is one proposed in a recent report of the Geological Survey.* The log of the borehole 
is appended.-f 

No. 1 Borehole, Waitangi Hill. 



Nil to 


20 ft. 


Yellow clay. 


At 16 ft. 




Struck water. 


20 ft. to 


40 ft. 


Yellow clay and mixed papa. 


40 ft. „ 


52 ft. 


»> 


52 ft. „ 


58 ft. 


J J 


58 ft. „ 


67 ft. 


Gravel and clay mixed, caving character. 


At 61 ft. 




Increase of water. 


67 ft. to 


88 ft. 


Sticky clay and papa mixed. 


88 ft. „ 


95 ft. 


Caving clay and papa mixed 


95 ft. „ 


100 ft. 


Mud strata. 


100 ft. „ 


114 ft. 


Sticky clay and papa. 


114 ft. „ 


127 ft. 


Papa. 


127 ft. „ 


140 ft. 


3) 


140 ft. „ 


151 ft. 


Papa and gravel mixed. 


151ft. „ 


164 ft. 


Mud strata. 


164 ft. „ 


170 ft. 


Sticky papa. 


170 ft. „ 


189 ft. 


Caving rotten papa. 


At 179 ft. 




Struck tree 5 ft. thick. 


189 ft. to 


195 ft. 


Caving papa mixed with sandstone. 


195 ft. „ 


200 ft. 


gravel. 


200 ft. „ 


210 ft. 


Caving papa. 



* Second Annual Report, N.Z. Geol. Surv., 1908, p. 35. 
t Inserted by .T. 11. Bell. 



At 204 ft. 


Struck gas- vein. 


210 ft. to 221 ft 


. Caving papa. 


221ft. „ 230 ft, 


,, 


230 ft. „ 265 ft, 


' j> 


265 ft. „ 280 ft, 


Blue caving papa. 


280 ft. „ 300 ft. 


,. 


300 ft. „ 311 ft. 


Caving decomposed papa. 


At 311 ft. 


Struck vein of gas. 


311 ft. to 324 ft. 


Caving decoinpo.sed papa. 


324 ft. „ 336 ft. 


99 


336 ft. „ 349 ft. 


99 


349 ft. „ 356 ft. 


Sandstone and papa mixed. 


At 350 ft. 


Struck strong vein gas (oil formation). 


356 ft. „ 365 ft. 


Blue papa. 


365 ft. „ 375 ft. 


Light slialc. 


375 ft. ., 387 ft. 


Sandstone and papn inixi-d. 


387 ft.. „ 395 ft. 


Hard shell. 


At 390 ft. 


Increase of gas. 


395 ft. to 405 ft. 


Dark papa. 


405 ft. „ 416 ft. 


99 


416 ft. „ 429 ft. 


)l 


429 ft. „ 444 ft. 


Blue papa (hard shell). 


At 440 ft. 


Increase of gas. 


444 ft. to 458 ft. 


Sandstone and papa. 


At 456 ft. 


Increase of gas. 


458 ft. to 474 ft. 


Sandstone and papa mixed. 


474 ft. „ 486 ft. 


Hard shell. At 478 ft. sandstone and limestone mixed 


486 ft. „ 501 ft. 


Papa. 


501ft. „ 512 ft. 


Caving papa. 


512 ft. „ 525 ft. 


Hard-shell sandstone. 


At 522 ft. 


Increase of gas. 


525 ft. to 537 ft. 


Green sandstone;. 


537 ft. „ 572 ft. 


Caving papa. 


572 ft. ., 582 ft. 


i> 


582 ft. „ 591 ft. 


Sandstone and papa inixctl ; increase of gas, 591 ft. 


591 ft. „ 601 ft. 


Sandstone and papa mixed. 


601 ft. „ 613 ft. 


>> 


613 ft. „ 622 ft. 


Dark papa. 


622 ft. „ 634 ft. 


j^ 


634 ft. „ 642 ft. 


Sandstone and papa mixed. 


642 ft. „ 652 ft. 


Dark papa mixed with limestone. 


652 ft. „ 664 ft. 


,, struck petroleum, 664 ft. 


At 655 ft. 


Oil in 1 ft. of grey sandstone. 


664 ft. to 677 ft. 


Caving papa. 


677 ft. „ 685 ft. 


Light caving papa. 


685 ft. „ 693 ft. 


Sandstone and papa mixed. 


693 ft. „ 700 ft. 


Papa and pug clay mixed, of a cement nature, struck. 


At 696 ft. 


Passed out of the oil-formation strata. 


700 ft. to 709 ft. 


Pug clay. 


709 ft. „ 716 ft. 


Pug clay cement gravel mixed, with limcutone boulders. 


716 ft. „ 729 ft. 


Cement gravel and pug clay. 


729 ft. ,.711 ft. 


,, 



741 ft. 


ti) 755 ft. 


755 ft. 


„ 770 ft. 


770 ft. 


„ 779 ft. 


779 ft. 


„ 789 ft. 


789 ft. 


„ 797 ft. 


797 ft. 


„ 806 ft. 


806 ft. 


„ 813 ft. 


813 ft. 


„ 8:20 ft. 


820 ft. 


„ 830 ft. 


830 ft. 


„ 844 ft. 


844 ft. 


„ 860 ft. 


860 ft. 


„ 872 ft. 


872 ft. 


„ 901 ft. 



Cement gravel and pug clay. 
Pug clay mixed with rubble. 



Hard papa strata, 8 ft. thick, struck. At 875 ft. ran into pug clay 
and rubble containing limestone of a cement nature. 
901 ft. Depth of the bore on the 2nd December, 1909. 

Physical Geography. 

The area included within the Whatatutu Subdivision consists, physiographically, of a 
series of rolling ridges of moderate height, separated by deeply cut river-valleys. There is 
one main water-divide running in a direction slightly east of north through the eastern 
portion of the subdivision from a point four miles due west of the south-eastern corner of 
the Waingaromia Survey District. 

The highest points on this main divide — namely, Ahititi (1,911 ft.). Arakihi (1,920 ft.), and 
Paraheka (1,867 ft.) — are, on the average, of 1,900 ft. lower elevation than those situated on 
the Raukumara Range, which passes through the north-western corner of the subdivision. 
These peaks are Little Mangahaumia or Big Slip (3,688 ft.), Mangahaumia (3,983 ft.), and Trig- 
onometrical Station M 4 (3,658 ft.). Thus it would appear that the area covered by the sub- 
division has a general slope in a south-easterly direction from the Raukumara Range towards 
the sea-coast. 

Two drainage-areas of unequal size are separated by the main water-divide. That to 
the west is by far the larger, and has been dissected by drainage-channels converging from the 
north, from the west, and from the east, to a point of junction about two miles below the median 
point of the southern boundary of the subdivision. The whole of this area is included in 
the watershed of the Waipaoa or Big River, whicli debouches into the western corner of Poverty 
Bay. The main Waipaoa River enters the subdivision close to the eastern boundary of the 
Mangatu Survey District and flows in a general southerly direction through the central portion 
of the area. In the vicinity of Whatatutu the Waipaoa is joined by the Mangatu River, which 
with its tributaries drains the country to the north-west and west, and by two left-hand branches 
—the Mangataikapua Stream and the Waingaromia River — which together drain the central 
and north-eastern portions of the subdivision. The Wheao Stream and the Waikohu River, 
which together drain the country to the south and south-west, and the Waihora River, which 
drains that to the south and south-east, are tributaries of the Waipaoa. junctioning with it 
outside of the subdivision. 

That portion of the subdivision to the east of the main divide is drained by the headwater 
branches of the Pakarae River. The main headwater branch, the Whakauranga Stream, 
rises on the main divide at Paraheka, and flows in a general southerly direction close to the 
eastern boundary of the Waingaromia Survey District. At a point two miles and a half west 
of Ahititi Peak it joins with the Mangarara Stream — which rises on the slopes of the peak named 
— to form the Pakarae River, flowing first east, then south, and debouching on the coast-line 
at the village of the same name. About the centre point of its course the Whakauranga 
Stream is joined by the Rosebud Stream, which drains an area between the peaks Arakihi 
and Parahek'i 



PLAIE I. 




.JLJf^^mik. 



\V.\IT.\N<;i ()ll.-H()l!K ON ( tl'i;MN(;-l).\Y. 




Waii'aoa Station, i.ooki.ni; Wkst a( lioss thk .\lAXf:Aru Fkkn Colntky. 
liiilhtin Xo. 5.] Wix-e V- «• 



9 

All the rivers and larger streams flow at grade In their middle and lower courses they 
are for the most part bordered by high- and low-level terraces. The most extensive low-level 
terraces are in the vicinity of the confluence of the Waingaromia and Waipaoa rivers, and 
on the lower stretches of the Waipaoa Kiver. 

A high-level terrace, forming a continuous flat-topped upland on the right or western 
bank of the Waipaoa River, stretches from the southern boundary of the subdivision to the 
village of WTiatatutu. From here it appears at intervals, continuing up the valleys of the 
Mangatu, Waipaoa, and Waingaromia rivers. This high-level terrace has in all cases an 
elevation of about 200 ft. above the water-level of the rivers. Evidences of the former ex- 
istence of a terrace, with an elevation 400 ft. higher than the present stream-beds, are to be 
seen in the valley of the Urukokomoku Stream, in the upper and in the lower portions of 
the Waipaoa River valley, in the Waingaromia River valley, and in the Mangaorango 
Stream valley. These terraces point to elevation of the area since the end of Miocene times. 
The Whatatutu Subdivision is at the present time undergoing a period of rest from tectonic 
movements, as evidenced by the facts that the larger streams and rivers are flowing at grade, 
and that their tributaries are rejuvenated streams which have in many instances cut back 
their hanging valleys for some distance from their confluences with the main streams at the 
same level. 

The general flat-topped appearance of the Tutamoe Ridge, about 3,000 ft. in height, and 
running in an east and west direction about one mile outside the northern boundary of the 
subdivision, the evidences near Wooler's homestead and near Tuarua homestead of the 
former existence of a flat on the crest of the present main divide, and the apparent general 
south-easterly slope of the area from the Raukumara Range towards the sea-coast suggest 
that the subdivision forms part of a dissected but complicated coastal plain. 

The drainage system of this area has evidently been influenced by its geological structure, 
as will be seen by a study of the maps accompanying this report. 

Slumps or landsUdes are very marked throughout this area. Slumping is shown on 
slopes of the ridges either by a steep slope at an angle of 35° to 45° for the first 150 ft. below 
the crest of the ridge, with a final slope at an angle of 15° to 5° to the stream-bed, or by a 
vertical rock face for 100 ft. to 200 ft. below the crest, with the slunii)ed material forming a 
kind of terrace before sloping gradually to the stream-bed. 

Outline of Geology. 
Geological Sequence. 

Almost the whole of the area under review is covered by the beds of the Whatatutu Series. 
These beds are all sedimentary, and, since the fossils contained in them are marine, were 
evidently deposited imder the sea. Microscopical examination shows that a considerable 
portion of their constituents has been derived from igneous rocks. 

The lowest beds of this series which are exposed within the subdivision are of clay-shale, 
associated with chalky limestone and glauconitic sandstone. 

The other members of the series (see table of formations in Chapter II) grade into one 
another so that it is often impossible to distinguish one particular bed from that occurring 
either immediately higher or immediately lower than it in the series. 

The Waipaoa beds consist of pumiceous deposits, the material of which was probably 
derived from some distance outside the subdivision. These deposits are in general loosely 
consolidated, but outcrops of somewhat compact nature are occasionally found which have 
evidently been laid down under water. 

Loosely consolidated and unconsolidated debris has formed the gravel banks and flood- 
plains of the river-beds, and is seen as a covering for the low-level and high-level terraces 
throughout the area. 



io 

Geological History. 

The area covered by the Whatatutu Subdivision has suffered periods of elevation and 
depression relatively to sea-level with intervals of rest. It is probable that the lowest beds 
of the Whatatutu Series were at a higher elevation in the north-western portion of the sub- 
division, probably representing a coastal plain with a downward slope from the Raukumara 
Range towards the south-east (see pages 12 to 15), when the younger beds of the series were 
being deposited. Owing to the gradations that occur between the members of the upper portion 
of the series, it is almost certain that they were to a great extent laid down contemporaneously. 
During this deposition elevation was in progress, the close of which is marked by the deposi- 
tion of conglomerate beds. A depression after that time would account for these beds being 
overlapped by argillaceous sandstones and claystones. The fact that the latter are co\ered 
by a fairly coarse sandstone would point to elevation ha%nng taken place after or during their 
deposition. Since all the beds of the series are apparently conformable, the folding of the 
rocks of the series evidently did not take place until after the last member was laid down — 
that is, at the close of the Miocene period. 

This folding evidently influenced the direction of the main drainage-channels of the area. 
During the interval of rest the main streams cut down their beds to grade and formed the 
present 400 ft. high-level terraces. A relative elevation of the area, probably gradual, of not 
less than 200 ft. then took place. This was followed by an interval of rest diiring which the 
rivers and main streams again cut down their beds to grade, and formed the somewhat exten- 
sive 200 ft. high-level terraces of to-day. A subsequent relative elevation of not less than 
200 ft., the last that has taken place, has been followed by an interval of rest of sufficient 
duration to allow the rivers and larger streams to cut their present courses down to grade. 

Literature. 
1874. Hector, J. : " East Cape District." Rep. G.S., 1873-74, vol. viii. On pp. x\i-xx 

of the introduction to this volume a brief account of the geology of an area including 

the Whatatutu Subdivision is given, together with a map and sections. Special 

reference is made to the occurrence of oil at Waitangi Hill. 
1874. Skey, W. : " On the Mineral Oils of New Zealand." Trans., vol. vi, pp. 252-59. 

Pp. 256-57 give a description and an analysis of sample of oil from Poverty Bay. 
1874. McKay, A. : " Reports relative to the Collection of Fossils made in the East Cape 

District, North Island." Rep. G.S., 1873-74, vol. yiii, pp. 116-64. Pp. 159-162 

have reference to the rocks occurring in the \'icinity of the oU-springs at Waitangi 

Hill and the collection of fossils from them. 

1876. Cox, S. H. : " Report on the Coimtry between Poverty Bay and Napier." Rep. G.S., 

1874-76, pp. 96-105. Some beds similar to those described also occur in the 
^\Tiatatutu Subdivision. 

1877. Cox, S. H. : " Report on the Country between Opotiki and East Cape." Rep. G.S., 

vol. X, 1877, pp. 106-13. Pp. 110 and 111 have reference to beds considered to 
belong to the oil-bearing rocks of Poverty Bay. 

1887. " Handbook of New Zealand Mines." This publication, compiled by Mr. P. Galvin, 

under the direction of the Hon. W. J. M. Larnach, then Minister for Mines, gives a 
complete account of mining in New Zealand at the time of its issue. P. 352 has a 
very brief reference to the oil of Poverty Bay. 

1888. Gordon, H. A. : " The Gisbome Oilfield." H.-3, 1888. This report deals vnth. the 

history of the attempts to establish a petroleum industry in Poverty Bay to that 
date, with remarks as to the future prospects of the industr\\ 
1888. Hill, H. : " The Oil Prospects of Poverty Bay and District." Trans, vol. xxi, 1888. 
pp. 320-25. This article gives a description and log of the South Pacific borehole, 
and has remarks concerning the future prospects of the oil industry of this 
district. 



11 

1888. Park, J. : " On the Oil-bearing Strata of the North Island." Trans., vol. xxi, 
pp. 489-92. P. 490 deals with the prospects of obtaining oil at Poverty Bay. The 
sites at which wells at that time were being drilled are condemned. 

1901. McKay, A. : " Report on the Petroleum-bearing Rocks of Poverty Bay and East Cape 
Districts." C.-IO, 1901, pp. 21-25. Describes the geological formation of an area 
including the Whatatutu Subdivision. Special reference is made to the probable 
source of the oil, and favourable localities for boring are indicated. 

1901. Neuberger and Noalhat : " Technology of Petroleum." 1901. P. 180 has a very 
brief note on the occurrence of oil at Poverty Bay. 

19(>(i. Sollas, W. J., and McKay, A.: "Rocks of Cape Colville Peninsula, New Zealand." 
Vol. i, 1905 ; vol. ii, 190G. In vol. ii, pp. 174-78, a description is given of the conglo- 
merate of this area. Six rock-sections cut from specimens of the constituents are 
described and identified. 

190fi. Redwood, Boverton : " Petroleum and its Products." First edition, 1901 ; second 
edition, 1906. The second edition, on pp. 103-104 and 191, refers briefly to the 
occurrences of oil in New Zealand. 

1906, " Handbook of New Zealand Mines." This publication, compiled by Mr. P. Galvin, 
under the direction of the Hon. James McGowan, then Minister for Mines, has on 
pp. 520-21 a brief reference to the oil of Poverty Bay. 

1908. Hill, H, : " The Great Wairarapa : a Lost River." Trans., vol. xli, 1908, pp. 429-37. 
This article propounds the theory that a great river, of which the Waipaoa River 
formed the head-waters, once flowed through Hawke's Bay. Reference is made to 
the pumiceoua deposits occurring in the Whatatutu Subdivision. 



12 



CHAPTER II. 



GENERAL GEOLOGY. 





Page 






Page 


Classification 


.. 12 


Structure — conlinued. 






The Whatatutu Series— 




General Structure 


. , 


24 


I. The Lower Whatatutu Beds 


.. 12 


Detailed Structure 




25 


II. The Upper Whatatutu Beds 


.. 15 


The Waipaoa Series . . 


. . 


32 


Palaeontology 


.. 21 


Loosely Consolidated 


and L'nconsoli- 




Structure — 




dated Debris 


. . 


32 


Introduction 


.. 23 


Faults 


. . 


32 



Classification. 
Owing to the fact that the area covered by the Whatatutu Subdivision represents but a small 
part of the Raukumara Division, the geological classification of the rocks submitted in this 
report, as applied to the whole division, can only be tentative, pending further detailed 
geological investigation in areas adjacent to that now under review. The following table gives 
the classification of the various strata compiled from a report* by McKay, who examined 
geologically a considerable portion of the Hawke's Bay Land District, and with it the classifica- 
tion made in this report : — 



Classification by McKay (1901). 



Classification in this Report. 



Age. 



Pctrological Cbaiacter. 



Age. 



Petrological Character. 



Middle Cretaceous 



Upper Cretaceous 



Lower Tertiary 



Pliocene 



Recent . . 



Sandstones and dark shales with 
concretions; limestones of yel- 
low tint. 

Greensands, siliceous shales ; 
indurated chalky limestones, 
alternating with greensands; 
marly limestones or calcareous 
sandstones. 

Coarse conglomerate or breccia, 
sandy and marly clays with 
beds of grey or yellowish- 
brown sandstone ; coralline 
foraminiferous limestone. 

Sandy clay, pumiceous sands, 

limestones. 
Alluvial deposits. 



y Upper Miocene -\ 

I 



J 
Pliocene (?) 

Pleistocene and Re- 
cent 



Whatatutu Series, — 
Lower — 

(1.) Clay-shale, chalky lime- 
stone, glauconitic sand- 
stone. 
Upper — 

(1.) Claystone and argil- 
laceous sandstone with 
concretions. 
(2.) Claystone and argil- 
laceous sandstone ; con- 
glomerate, limestone, 
fossiliferous argillaceous 
sandstone ; coarse sand- 
stone. 
Waipaoa Series : Pumiceous de- 
posits. 
Loosely consolidated and uncon 
solidated debris. 



The Whatatutu Series. 

The Whatatutu Series, on account of palaeontological evidence, and from the fact that 
no marked stratigraphical unconformity was observed between any of its members, is regarded 
in this report as a continuous series of Upper Miocene age. Mainly for the sake of convenience 
in description it has been subdivided into (I) Lower, and (11) Upper Whatatutu Beds. 

I. The Lower Whatatutu Beds consist of clay-shale, chalky limestone, and glau- 
conitic sandstone. 

Clay-shale. — As described on page 30, beds of clay-shale occur in the head-water branches 
of the Waitangirua and Mangatahu streams — that is, in the extreme north-west corner of 
the subdivision. 



* " Report on the Petroleurii-bearing Rocks of Poverty Bay and East Cape Districts." C.-IO, 1901, pp. 21-25. 



Sh nrrfynparvf Btillctirv 2^0. WTmitxtiiiii S\thdiyistfm,,'R.aJjkwnAirajI)ivisWTV.Ma.y,kesBnyLmtA Bistrt^t 



D 





"Baajds shovfTh thu,3 - — ^^ «=' 

Tri^.Statiaris , „__©orO 

Confflffm^ratr^ancLs ., X 

KxCCtutI Gas Vents „ • 

ProjxjsedSorvt^ Sites- _ ,, ® 

Sprviga , ^ 

OuJxrops wiOj. observed^ strike ^ <ii.p A*. 



GEOLOGICAL MAP OF 



UPPER 
MIOCENE\ 



Whatatui 
Clay shale, chalky I 
^lauconitic sandetone. 
Claystone ar>d arjillace 



JAMES MACKINTOSH BELL 



18 

Three zones of slightly different character were observed during the course of the survey.. 

The lowest is a brown-black rock of clayey appearance, composed of finely comminuted, 
loosely compacted grains, and is thus broken up readily by atmospheric agencies. This rock, 
when pulverised and strongly heated in a hard glass tube, gives off a small amount of gaseous 
hydrocarbons, while small globules of liquid hydrocarbons form on the cooler parts of the 
tube. A sample submitted for analysis gave the following results : — 

Silica (SiOj) . . . . . . . . . . . . 6300 

Alumina (AI2O3) . . . . . . . . . . . . 16-08 

Iron-oxide (FeaOg) . . . . . . . . . . . . 2-28 

Lime (CaO) . . . . . . . . . . . . 0-82 • 

Magnesia (MgO) . . . . . . . . . . . . 1-40 

Moisture and organic matter . . . . . . . . 13-51 

Alkalis and undetermined . . . . . . . . . . 2-91 



100-00 
From this analysis it will be seen that the rock consists mainly of silicate of alumina 

In one of the two outcrops in the Mangatahu Stream this clay-shale was found to contain 
small nodules of pyrite (FeSj). It is reported that similar rock occurs in the Waitangirua 
Stream, and nodules of pyrite obtained from it were seen by the WTiter. 

The second zone outcrops in the head-water valley of the Waitangirua Stream. In a 
cliff-face it is exposed for a height of about 150 ft. covered above by the highest zone. The 
shale here is a hard, finely textured rock of grey colour, built up of very thin laminae, and 
breaking readily into thin flakes when struck with a hammer. 

The third or highest zone is a hard, finely comminuted rock of grey colour and faintly 
crystalline appearance. It breaks easily under the hammer into thin flakes, but does not 
disintegrate readily on exposure to the air. This rock when finely pulverised and strongly 
heated also gives a smell of hydrocarbons ; but the smell is not so strong as that obtained 
from the rocks of the lowest and middle zones. An estimation of the amount of carbonate 
of lime contained in the rock gave 4-06 per cent. It contains numerous Foraminifera, and, 
even without the aid of the microscope, shows casts of Nodosaria. 

On the Mauiigahaumia track and in the Mangapapa and Mangamaia streams occur expo- 
sures of calcareous claystones, intermediate in character between clay-shale and chalky lime- 
stone. In general these rocks have an earthy appearance. Their colour is usually grey, 
l)ut tints from green to brown are shown as the proportion of included carbonaceous matter 
increases. They exhibit an obscure lamination marked by irregular streaks where carbonaceous 
matter separates the lamina?. They are fine-grained in texture, and have a moderate hard- 
ness. All contaiii a greater or less proportion of carbonate of lime, and often show thin veinlets 
of calcite. In some cases small grains of pyrite are included with the carbonaceous material. 

Examined under the microscope the main constituents of the calcareous claystones are 
kaolinitic matter, calcite, and feldspar, with a few grains of quartz and viridite. Foramini- 
fera are fairly abundant. 

A typical sample of these rocks intermediate between clay-shale and chalky limestone 
was submitted for analysis, and gave the following result : — 

SUica (SiOo) 40-07 

Alumina (AI2O;,) 11 90 

Iron-oxide (Fe^O.) . 1 68 

Lime (CaO) . . . . 2100 



Magnesia (MgO) 

Phosphoric anhydride (P_,0.) 

Carbonic anhydride, moistui'e, and organic matter 

Alkalis aud uadctcrmincd . . . . 



1-20 

0-15 

21-60 

2-JO 

1(J0-0(J 



14 

This analysis may be compared with analyses 2, 3, and 4 of chalky limestone (p. 44) 
and of clay-shale (p. Mi). 

Chalky Limestone. — The exposures of chalky limestone extend dver a moderately large 
area in the subdivision. The largest continuous outcrop is in ihf north-western portion, 
where it covers the greater part of an area, about six miles in length and five miles in width, 
lying immediately to the west of the Mangatu River bed. A portion of this area is covered 
by glauconitic sandstone in the headwater valleys of the Mangamaia and Makerewau 
streams (see p. 30). 

Chalky limestone is exposed on the crest of the Waitangi anticline, in the Waipaoa River 
bed, and in the valley of the Mangataikapua Stream (see p. 28), and also on the eastern 
slopes of the dome of the Toromiro anticline (see p. 26). 

The rock has a finely crystalline texture. Typically its colour is chalky white, often, 
however, tinted red, brown, or green by ferruginous minerals. Since the rock breaks readily 
into irregular flakes and cubes by exjiosure to atmospheric agencies, all its outcrops are irregu- 
larly jointed and broken. For the most part veinlets of calcite traverse the exposures, and 
occasionally attain a thickness of 3 in., but in general they are mere thread-hke partings. 

The results of the analyses of chalky limestones are given on page 44 (Nos. 2, 3, and 4). 

With the exception of one specimen of Dentalium gujanteum no fossil MoUusca were ob- 
served in the chalky limestones. Sections examined microscopically show that they contain 
numerous Foraminifera. 

Many exposures, examined in the field, appear to be lithologically similar to the chalky 
limestones, but the results of analyses of samples show that they contain a very high per- 
(••entage of silica and a low percentage of carbonate of lime. A sample obtained from the 
rocks exposed in the Mangatu Gorge contained only 2-02 per cent, of carbonate of lime. The 
results of the analyses of two samples of these siliceous rocks (1) from head of left branch of 
Makara Stream, and (2) from head of right branch of Te Hau-o-te-atua Stream, are here 
appended : — 

Silica (SiOo) 
Alumina (AI2O3) . . 
Iron-oxide (FejOa) 
Lime (CaO) 
Magnesia (MgO) . . 
Carbonic anhydride (CO 2) • • 
Moisture and organic matter 
Alkalis and undetermined - . 

100-00 100-00 

The microscopical examination of sections of these rocks shows that the main portion of 
this silica is secondary. It is probable that the greater portion of the original carbonate of 
lime in the limestone has been replaced by silica derived from infiltrating meteoric waters. 

Glauconitic Sandstone. — A continuous outcrop of glauconitic sandstone is exposed in the 
head-water valleys of the Mangamaia and Makerewau streams, and in the head-water valleys 
of the right-hand branches of the Mangatahu Stream (see " Structure," p. 30). It also 
occurs in the crest of the Waitangi anticline, at and in the vicinity of the Pulpit Rock (see 
p. 28), and in the valley of the Mangataikapua Stream. 

The exposures of glauconitic-sandstone rock have in general a leek-green colour on 
unweathered surfaces, changing to dun colour where they have been oxidized by exposure 
to atmospheric agencies. The texture is moderately coarse, and occasionally the glauconite 
grains attain a diameter of ^^ ^^• 

The exposures of glauconitic sandstone vary somewhat in the western and eastern por- 
tions of the subdivision. To the west of the Mangatu River the rocks are often laminated, 



(1-) 


(2.) 


. . 75-20 


83-20 


4-32 


5-80 


2-68 


4-50 


6-56 


1-54 


0-40 


0-30 


5-25 


1-23 


2-35 


3-00 


3-24 


0-43 



15 

and in general show stratification. To the east of the same river they are massive, with thin 
veinlets of calcite and in a few cases with small lenses of rock crystal and cherty material. 

In the bed of the Mangamaia Stream an exposure of about 30 chains contains concre- 
tions of iron-oxide up to an inch in diameter. At the Pulpit Rock carbonaceous matter is 
included in the rocks and some scattered specks and patches of pyrite or marcasite. 

The glauconitic sandstones do not appear to be fossiliferous. The glauconitic grains 
may have formed in the spaces left after the removal of Foraminifera from sandstones, but 
such sections of the rock as were microscopically examined do not show this to be the case. 

Rocks which have a character intermediate between glauconitic sandstones and clay- 
stones occur in the Urukokomoku Stream bed. They are moderately coarse-grained rocks 
of a greenish-black colour, showing no definite structure. They are fairly soft, and carry only a 
small percentage of lime. The grains of glauconite are very small. Calcite veinlets often 
occur in these intermediate rocks, and occasionally some carbonaceous matter may be seen. 
The result of an analysis of a sample of a transition rock between glauconitic sandstone 
and claystone is appended : - 

Silica (SiOj) • • • • ■ • • • 57-35 

Alumina (AI2O3) 14-42 

Iron-oxide (FeaOj) . . 3-28 

Lime (CaO) .. .. fSS 

Magnesia (MgO) 2-01 

Phosphoric anhydride (P,(),) .. .. 0-16 

Carbonic anhydride, moisture, and organic matter . . . . 12-20 

Alkalis and undetermined . . . . 2-i)(/ 



100-00 



Under the microscope the rocks show fragments of feldspar and (|uar, z as the predominant 
constituents. Grains of glauconite are fairly abundant. The cemcniing material is inainiy 
nondescript kaolinitic matter, together with iron-oxide. 

II. The Ui'per Whatatutu Beds consist of (1) claystone and argillaceous sandstones 
with concretions ; (2) claystone and argillaceous sandstone, conglomerate, limestone, fossili- 
ferous argillaceous sandstone, and coarse sandstone. 

With the exception of the beds of conglomerate and of limestone, all the members of 
the Upper Whatatutu are popularly termed " papa."* Thus the term " papa " includes 
rocks from claystone to sandstone, and on account of this wide meaning has not been used 
in the text of this report, except under the heading of " Materials for Macadamising Purposes " 

(1.) Claystone and argillaceous sanrtsltme icith concretions occur mainly in the eastern 
portion of the subdivision. No contact between these rocks and the glauconitic sandstone 
has been obser\ ed, but from their occurrence with reference to those beds which are considered 
to be higher in the series, as described under the structure of the Whatatutu Series (pp. 25 
to 31), they have been placed in a separate group from the latter. 

In only a few exposures do the daystones and argillaceous sandstones show stratification 
so that their conformity or otherwise to the overlying beds cannot be judged from the direction 
of the dip. 

The Waingaromia and Waihora rivers, the Waitangi, Tawa, Parariki, Makahakaha, 
Ngarara, Kawakawa, Toromiro, Te Hinahina, and Wheao streams, all show some exposures 
of these beds. Detailed reference to these outcrops is given in the description of the Waitangi 
anticline (p. 27) ; the Waingaromia syncline (p. 27) ; and the Toromiro anticline (p. 26). 



* " Pivpa " is a word common to the NLiori iind Polyuesiiin languages, and it« meaning in general as api)lied 
to rocks implies flatness. An extended use of it in JLiori refers to a " kind of soft stone resembling indurated 
pipeclay," " a hard sandstone rock, layers of which, set in a frame, are used for polishing and grinding green- 
stone." 



16 



The claystones are fine-grained rocks which suffer considerably from surface decompo- 
sition. Where they occur in cliff-faces, talus slopes are always to be found. In colour they 
varj' from grey to dark brown, showing almost black when wet. They break easily in 



any direction, and the material forming the talus slopes is generally in rough cubes, 
usually contain a small percentage of lime. 

The result of an analysis of a typical sample of claystone is appended : — 

Silica (SiOj) 

Alimiina (AI2O3) 

Iron-oxide (¥6203) . . 

Lime (CaO) 

Magnesia (MgO) 

Phosphoric anhydride (PoO.) 

Carbonic anhydride, moisture, and orgar 

Alkalis and undetermined 



They 



[lie matter 



52-97 
18-84 
2-32 
7-89 
1-96 
0-16 
12-69 
3-17 



100-00 

Argillaceous sandstone is intermediate in texture between a claystone and a sandstone. 
In colour, hardness, and fracture the argillaceous sandstone of this area strongly resembles 
claystone. Its texture is, however, somewhat coarser. 

The concretions which occur in the Upper Whatatutu beds are calcareous or dolomitic. 
They are commonly found as boulders as much as 5 ft. in diameter, and as irregularly cylindrical 
masses with a diameter up to 9 in. and a length of from 1 ft. to 20 ft. They also occur as curved 
cylindrical masses tapering in diameter from 6 in. to 1 in., with a maximum length of about 
5 ft. 

Both the calcareous and the dolomitic varieties have in general a brown-black colour, 
and are extremely fine-grained. They show an uneven to conchoidal fracture. 

The actual nucleus of these concretions was not determined in any specimens, and is 
no doubt variable. Grains of sand, pebbles formed of sandstone, or some vegetable matter 
probably formed the nuclei of many of them. Vegetable matter as a nucleus would account 
for the great length attained in some instances. 

The central portion of many of the concretions shows a core about 1 in. in diameter, 
surrounded by a covering of iron-oxide. 

It is stated by McKay* that these concretions at Waipiro Bay and along the coast-line 
northward contained specimens of the fossils Inoceramus : though careful search was 
made, no concretions were found within the subdivision containing specimens of this fossil. 

In the left-hand headwater branch of the Waitangi Stream boulders of chert-breccia 
occur in the claystone, in addition to the concretions described above. These boulders of 
chert-breccia attain a maximum diameter of 3 ft., and are composed of more or less angular, but 
sometimes rounded grains and pebbles of chert. These pebbles are often as much as 6 in. across. 
The cementing medium is of carbonate of lime, for the most part visibly crystalline. 

Sections of concretions when examined under the microscope show dolomite and kaolinitic 
matter as the main constituents, with a few grains of quartz, and a small amount of altered 
feldspar, . - 

(2.) Claystone, argillaceous sandstone, conglomerate, limestone, fossiliferous argillaceous 
sandstone, coarse sandstone togeihei: cover about three-quarters of the area of the Whatatutu 
Subdivision. The claystone and ariiillaccous sandstone are similar to those described m the 
last group. These beds, however, contain no concretions, and are always stratified. In 
general the argillaceous sandstones are associated with claystones, though in many cases 
the- former occur alone, the bedding-planes being often indicated by a slight impregnation 
with iron-oxides. 



* tJco >Iiiies lioporl. 6.-I0V 11X)1, ]>. 23. 



17 

As these beds are found ()\er a large area, it is only reasonable to expect that all the 
exposures should not be identical. In different localities different conditions of deposition 
liave given rise to slight variations in tiie texture of the deposits laid down, so that the 
claystones and argillaceous sandstones are found at times to be interstratified with bands of 
sandstone, limestone, shelly conglomerate, or indurated material. 

The sandstone bands vary in thickness, attaining a maximum of 2 ft. They have in 
general a light-brown colour, and the texture of the grains is coarser than that of the argil- 
laceous sandstone. These bands are of fi'equent occurrence. 

Limestone bands interstratified with the beds of this group occur but rarely. On the 
summit of Wheturau Hill an outcrop, some 15 ft. in thickness, is seen extending from Trigono- 
metrical Station 138 westward along the ridge for a few chains. From this outcrop specimens 
of Ostrcn iHfjoiK* some 9 in. in length were obtained. In the bed of the Waipaoa River, on 
the right l)aMk opposite Waipaoa homestead, a band of limestone some 3 in. or -1 in. thick 
is interbedded with argillaceous sandstone and claystone. Similar l)ands about 10 ft. in 
thickness, associated with the same beds, were observed on the crest of the ridge separating 
the Waipaoa River and the Mangaorango Stream, slightly south of east from the mouth of 
the Weraroa Stream, and also on the crest of the same ridge about one mile farther eastward. 
These limestones are fairly crystalline in character and have a greenish tint. They 
contain numerous small shell-fragments and a very small proportion of sand-grains. 

Shellif cnni/lDmcrate bands occur in the beds of the Waipaoa River, and in the Manga- 
tuamaru, Torekepokia, Mangataua, and Omega streams. These bands are of a loosely coherent 
nature, and consist mainly of shells and shell-fragments, with some small pebbles of sand- 
stone and a verv small propoi-tion of sandy clay. The average thickness of the bands is about 
6 in., and the maximum attained is about i) in. 

Indurated bands are of frequent occurrence in that part of the Upper Whatatutu Series 
iu)W under consideration. In the bed of the main Waipaoa River they occur interstratified with 
argillaceous sandstone, and, towards the confluence of this river with the Waingaromia River, 
with argillaceous sandstone and claystone. In the bed of Branch A of the Mangaorango 
Stream the exposures show argillaceous sandstone in bands of from 5 ft. to 10 ft., separated 
bv indurated bands 1 ft. in thickness. The Ruahine, Clover Flat, and Makara streams have ex- 
posures showing these bands with a thickness of 1 ft., associated with argillaceous sand- 
stone and claystone. In the Pukekuri, the Wheao, and the lower portions of the Mangamaia 
and Mangapapa streams they occur with argillaceous sandstone ; in the Waikohu River 
with argillaceous sandstone and claystone, and with the exposures of conglomerate (see p. 1!») ; 
in the Mangatuamaru, the Torepokia, and Omega streams indurated bands are interbedded 
with claystone, argillaceous sandstone, and shelly conglomerate bands ; and in the Mangataua 
and Tawa streams with argillaceous sandstone and claystone. The many waterfalls of the 
latter stream are in part due to the greater resistance that these bands, as compared with 
the associated beds, offer to denudation. 

On the Gisborne-Waiapu Inland Road, in the vicinity of Paraheka Peak ; on the Wcst- 
Ho Track ; in the beds of the Motumate, Hinakiwawahia, and AVhakauianga streams, these 
bands are interbedded with the fossiliferous-argillaceous sandstone, to be described later. 

In the extreme head-waters of the Waitangi Stream indurated bands are interstratified 
with claystones, and at a higher elevation, on the crest of the ridge at the head of this stream, 
with coarse sandstones, the highest member of the series. 

In some instances these bands are fairly hard, very fine-grained rocks of a brownish- 
black colour, and probably represent bands of claystone hardened by the deposition of 
dolomite from infiltrating solutions. In general, however, they consist mainly of shells and 
sliell-fraiiments, cemented togetlier in a matrix of dolomite or calcite containing a small pro- 
])ortion of sand-grains and clav. 

* Not inr.liulcd in the list <>f fossils i^ollcctt-d by Ur. Jlarsliall. for which see pages 21 to 23. 
2— Whatatutu. 



18 

Conglomerate. — The conglomerates have the most distinctive characters of all the beds 
of tlic Whatatutu Series, and can be recognised without difficulty in any part of the subdivi- 
sion in which they occur. 

From the relative position of the exposures of these beds il is almost certain that they 
arc portions of an originally continuous stratum extending for some seventeen miles within 
the subdivision. This stratum would nppear to have been laid down on a shore-line which 
had the form of an arc of a circle with its convexity towards the north-west. This ancient 
shore-line extended from Atarau Stream westward to Conglomerate Stream, then south- 
westward across the Mangatu River in the vicinity of Te Hua, Otamaharama, and Makerewau 
streams, onward past Trigonometrical Station M 1, across the Mangamaia and Mangapapa 
streams, then southward across the Urukokomoku and Wheao streams to the Waikohu River. 
The original shore-line probably continued southwards, and possibly eastwards, beyond the 
limits which have been indicated. 

The conglomerate beds have been included in the general folding of the area, and no 
longer form a continuous stratum, since portions have been removed by denudation, especially 
from the crests of the anticlines. 

The most easterly exposuie of these beds is that in the waterfall of Atarau Stream (see 
map of Waingaromia Survey District). The beds here consist of pebbles and boulders, mostly 
of igneous origin, but some are portions of concretions derived from older beds of the Whata- 
tutu Series. The igneous pebbles are waterworn, and the maximum size attained is 1 ft. in 
diameter. In this exposure the beds have a general north-and-soutli trend. They probably 
are continuous northward from Atarau Stream, as at a distance of three-quailers of a mile 
in that direction large boulders of similar conglomerate appear in the Mangaorango Stream bed 
and on the slopes to the eastward of the stream. The occurrence of rounded igneous boulders 
in the extreme head-water branch of the Waitangi Stream may point to an extension of these 
beds in a southerly direction. 

On the eastern slopes of the Makara anticline boulders and pebbles of igneous conglomerate 
occur in branches D and E of the Mangataikapua Stream. 

On the western slopes of this anticline conglomerate beds are exposed in Conglomerate 
Stream. In the stream-bed below the stock-track bridge the lowest portions of the exposure 
are of comparatively finely textured material, the largest grains being about | in. in diameter. 
These beds are covered by argillaceous sandstone and claystone for a thickness of some 20 ft., 
and overlying the latter are beds of conglomerate with a thickness of about 120 ft. The texture 
of the material contained in these beds varies, but it is noteworthy that on the whole it increases 
in coarseness from the lowest layers up to the highest. In the upper beds the average diameter 
of the material is about 2 in. and the maximum diameter about 2 ft. These pebbles and 
boulders, as in the exposure of Atarau Stream, are mainly of igneous origin. Small pieces of 
cjuartz, of indurated sandstone, and of indurated claystone, also occur. The beds, trending 
slightly to the west of north, are also exposed towards the head of Conglomerate Stream ; 
while boulders of conglomerate occur on the crest of the ridge on which Wheturau Hill 
is situated, and on its northerly slope to Homestead Stream (see also p. 29). 

Igneous pebbles and boulders occur in the Te Hua and Otamaharama streams, and pro- 
bably represent the remains of the continuation of the conglomerate stratum on the eastern 
slope of the Mangatu anticline. 

With the exception of a few igneous pebbles occurring in the Makarewau and Mangamaia 
streams, no evidence of the existence of conglomerate beds is seen until the Urukokomoku 
Stream is reached. Here, in the stream-bed, a mile and a half above its mouth, bands of 
conglomerate of fairly fine texture are associated with bands of argillaceous sandstone. 

Th<ese bands are probably continuous over the crest of the Wheao anticline, as pebbles 
and boulders of igneous material occur in the Wheao Stream, and an exposure nearly a mile 
in width is to be seen in the Waikohu River bed about due south of Trigonometrical Station 2. 
This exposure consists mainly of very finely textured conglomerate, which for some distance 
on the right-hand bank of the river forms a cliff-face over 100 ft. in height, showng beds 10 ft. 



19 

to 15 ft. ill thickness, separated by somewhat indurated argillaceous sandstone bands. The 
constituents of tlie beds in this exposure are similar to those of exposures described above. 

The chief geological interest in this conglomerate arises from the fact that many of 
the igneous pebbles that form the greater portion of it diSer in character from any igneous 
rocks that have so far been obtained in situ in any part of the North Island of New Zealand. 
No theory as to their derivation, based on the data available at the present time, can be 
other than speculative. McKay,* who examined this conglomerate, stated with regard to 
its igneous constituents, " Their origin is obscure, and the speculation that the bulk of the 
material forming the conglomerate has been carried by ice from the CoUingwood district of 
Nelson is tenable only for lack of a better explanation of the facts." 

In the opinion of the writer the theory of ice transportation is not tenable under any 
conditions. The constituents of the conglomerate, by their well-rounded appearance from 
the finest to the coarsest portions, show that they have been subjected to wearing, such as 
would be the result of their having been transported by running water or sorted by wave- 
action. As further evidence of theii liaving been sorted by the action of water, it may be 
stated that the lavers of conglomerate in most cases have beds of finely textured sediments 
associated with th(!m ; the exposures are made up of a number of beds the texture of which 
increases in coarseness from the lowest upwards ; the constituents of the individual beds 
do not show the irregularity in size that would be expected from material transported by 
ice, but are in all cases fairly uniform. No striations were observed on any of the pebbles 
and boulders contained in the beds. 

With the data at present available it is impossible to state the locality from which the 
igneous constituents of these conglomerates have been derived. The occurrence, however, 
in the Otamaharama Stream of an igneous boulder 10 ft. in diameter would suggest that 
these materials have not been transported any great distance. 

Should the detailed geological examination of the crest and eastern slo|)es of the Rau- 
kumara Range between Mangahaumia and Hikurangi mountains throw no light on the deriva- 
tion of these igneous rocks, the study of the occurrence of the granite boulders in the King- 
countryt and of the syenite porphyr}' of KawhiaJ might aid somewhat in arriving at a more 
definite conclusion. 

A microscopic examination of six specimens of the pebbles and boulders contained in these 
beds was made bv Professor Sollas,§ who determined them as follows : — 

(1.) Hornblende-plagioclase rock, very possibly a transformed dolerite or gabbro. 
(2.) Altered andesite with doleritic structure, or it might lie termed a diorite. 
(3.) Pyioxene-hornblende-giK'iss. 
(4.) Basalt containing some biotite. 
(5.) Hornblende-gneiss containing augite. 
(6.) Hornblende-augite-gneiss. 
Rock-sections cut from nine specimens obtained from these congioniciale beds during the 
present survey were examined microscopically. Brief descriptions of the rock species obtained 
are here appended : — 
(1.) Basalt. 

A glassv vesicular basalt, showing conspicuous amygdules of calcite slightly over 
I in. in diameter (similar to No. 4 above). 
(2.) Tuflf. 

A curious rock consisting in the main of alkali feldspars, a minor amount of alkali- 
lime feldspar, and quartz. Calcite forms a cementing material between the 
grains, and has been deposited by infiltrating-solutions. 

* " Rocks of OA\n- Colvillc Peninsula. New Zealand," vol. ii. 1906, p. 178. 

t ■• (Iranit*- Roc^ks in the Kin<;-conntry," .1. Park. Trans. 1802, vol. xxv. yy. :j.53-i)2. 

X " The G<-olony of the Kawhia District." Re-]). G.S., 1883-84, vol. xvi. p. 146. 

§ " Rocks of Cape Colville Peninsula, New Zealand," SoUas and McKay, vol. ii, 190(), pp. 174-78 

2'— Whatatutu. 



•20 

(3.) Hoinblende-plagioclase rock. 

This rock is in the main liolociystalline, consisting of gieenish amphibole passing 
into a colourless decomposition product, and fairly basic plagioclase — between 
andesine and labradorite. Certain portions show the pilotaxitic structure 
of andesites. These may cither represent inclusions or differentiation areas. 
(4.) Diorite (more or less gneissoid). 

A peculiar feature of this rock is that the plagioclase has a wide range — from an 
acid t}'pe to a basic. Some untwinned crystals may be secondary orthoclase 
or valencianite. The section shows strain phenomena under crossed nicols. 
(5.) Dolerite. 

Macroscopicallv this rock appears to show olivine, but none was observed in the 
section. The chlorite present may have been formed by the decomposition of 
this mineral. Microscopically the structure is doleritic. Augite is plentiful 
in the section. The plagioclase is peculiar in that it is an acid variety approach- 
ing oligoclase. This section is somewhat similar to (9). but is coarser and 
shows little or no serpentine. 
(G.) Diorite. 

A holocrystalline rock consisting of hornbleude and plagioclase (labradorite) in 
about equal proportions. 
(7.) Altered dolerite (?). 

The characteristic minerals of this section are a greenish hornblende without 
idiomorphic crystals, and plagioclase occurring mostly as laths without 
definite arrangement. The plagioclase perhaps predominates. There is also 
a good deal of magnetite. 
(8.) Diorite. 

A fairly coarse-textured normal diorite. 
(9.) B;!S;dt. 

This section presents the finely crystalline structure common in some basalts. 
The feldspars, however, have a low extinction, and may be oligoclase. Fibrous 
serpentine occurs in definite patches throughout the rock, and shows spheru- 
litic structure under crossed nicols optically positive in direction of length 
of fibre : it probably represents altered olivine. 
Limestone. — This bed of the upper portion of the WTiatatutu Series occurs in somewhat 
isolated outcrops \\dthin the subdivision. On the right or northern branch of Limestone Stream 
(right-hand branch of Tawa Stream) it occm-s overlying argillaceous sandstone. It forms 
the summit of Saxby Hill, and the summit of Trigonometrical Station 1, Waikohu Survey 
District (about a quarter of a mile south of the subdivision). These outcrops are all situated 
to the east of the conglomerate beds, and while the latter were being deposited on the supposed 
shore-line, the former were probably formed contemporaneously in deeper water. The outcrop 
on Trigonometrical Station 1 is situated in fairly close proximity to the exposure of conglo- 
merate in the Waikohu Eiver. It contains very small pebbles of igneous origin, and was 
no doubt laid down sufficiently near the land to include some of the material which was then 
forming beds immediately adjacent to the shore-line. In general the rocks are composed almost 
entirely of shells and shell-fragments. They are of a pinkish-white colour, and very compact. 
Examined microscopically they are seen to be composed mainly of the shells of Brachiopoda 
and Pelecypoda with a few Foraminifera {Rotalia and others). The result of an analysis 
of a sample of these rocks is given on page -U (see No. 1). 

Fossiliferous Argillaceous Sandstone. — Beds of fossiliferous argillaceous sandstone are 
exposed for the most part in the western and south-western portions of the area. They form 
the main part of the outcrops in the head-water valley of the Waihora River, and of that 
portion of the area situated to the east of the main divide. In places they contain indurated 
shelly bands. 



21 

Specimens of CucuHcea alta were collected from these beds, but are not included in the fossils 
examined by Dr. Marshall. (See page 22.) 

These rocks are in general similar to the argillaceous sandstones which have already 
been mentioned (see page 16), but in almost every exposure they are fossiliferous. Not 
improbably they have been formed contemporaneously with some of the beds described 
above. 

Coarse Sandstone. — Beds of coarse sandstone appear to be the closing member of this 
series. On the summit of Atarau Peak coarse sandstones outcrop, with the lower beds inter- 
stratified with indurated shelly bands. The crests of the spurs between the branches of Tawa 
Stream are formed of coarse sandstone, and in one case are seen to be overlain by the beds 
of the Waipaoa Series. On the crest of the main divide coarse sandstone is in some cases 
found overlying the fossiliferous argillaceous sandstones. 

These coarse sandstones are of a light-brown colour, and the constituent grains are fairly 
uniform. There is but little cementing material between the grains, so that tliey arc looselv 
compacted, and break down readily to sand and sandy clay. 

A similar sandstone, but containing grains of viridite and glauconitc, forms the crest 
of the Wheao anticline in its western portion. These beds are exposed on the Te Karaka - Motu 
Road and extend northwards as far as the ridge separating the Wheao and Urukokomoku 
streams. In the extreme head-water valley of the Wheao Stream they dip at an angle of 
45°, and overlie argillaceous sandstone and claystone beds. Farther westward, in the valley 
of the Ngamangatawa, very well-stratified exposures are found. Some bands in these ex- 
posures contain a sufficiently large amount of glauconite or allied mineral to give a deep-green 
colour to the rocks. 

Pal.eo.vtology.* 

The daystones which are the most abundant rocks of this area are usually not fossiliferous, 
or contain few and poorly preserved fossil remains. Locally the claystones grade into chalky 
limestones on the one hand and into sandstones on the other. Both of these rock-types are 
in several places fossil-bearing, but the number of individuals and species is far larger in the 
latter type. Even in such cases the fossils are strongly cemented to the compact sandstone, 
and are extracted with difficulty and often in a fragmentary condition. Identification is 
therefore somewhat difficult. 

The localities in which fossils were most abundant were, — (a.) Close to the mouth of 
the Tawa Creek, but on the opposite bank of the Waingaromia, where a band of shelly sand- 
stone crops out, from which numerous l)oulders have fallen down into the bed of the river. 
(b.) Atarau Peak : Here the sandstone which contains fossils is hard, and it is difficult to 
extract specimens sufficiently perfect for identification, (c.) The head-water streams of Te 
Hau-o-te-atua Creek, near the oil-springs on Waitangi Hill, (d.) Limestone Knob, at the 
head of the right branch of Tawa Creek. 

Although the species were represented in different proportions in the different localities, yet 
most of the dominant species were present in every outcrop. It is considered that the great 
differences in the stations at which the organisms grew were quite sufficient to account for that 
variation in the nature of the fossil remains that has been observed in the localities from which 
selections have been made. In other words, the fossils are not sufficiently different to indicate 
that portions of the rock-series are of a different geological age from other portions. It may 
be mentioned that this conclusion is supported by stratigraphical work, which has shown 
that the rocks belong to one conformable series. 

That the vital conditions of the stations at which the organisms lived were variable is 
dearlv shown by the nature of the deposits in which the fossils are imbedded. The variation 
from chalky limestone to claystone, and still further to sandstone, is certainly indicative of 
different depth and clearness of water and of greater or less proximity to the shore-line. 

* Report specially prepared by Professor P. Marshall, Otago University. 



2-2 

These considerations show that it is inadvisable to particularise the fossils of each locality 
separately, for the whole group of rocks must be considered as a pakeontological unit. The 
change from one rock-type to another is often abrupt, and frequently within a thickness of a 
few feet the rock changes back to the former type. It is thus seen that the change of conditions 
during deposition was of a most temporary nature. 

The following fossils have been collected from the rocks : — 



Mammalia : — 

A small piece of bone, probably 
of a whale. 
Gastropoda : — 

Conus (sp. ind.). 

Genota robusta. 

Olivella novozelandica. 

Scaphella gracilis * 

Scaphella elongata* 

Scaphella attenuata. 

Scaphella kirki* 

Fusus plebeius. 

Peristernia loevirostris. 

Fusus spiralis. 

Siphonalia conoidea* 

Lotorium olearium* 

Cassidaria senex. 

Cassidaria sulcata. 

Struthiolaria calcar. 

Turritella rosea* 

Natica gibbosa. 

Natica callosa. 

Natica ovaia. 

Crepidula incurva. 

Calyptrcea calyptrceiformis. 

Rotella zelandica.* 

Astralium (cast). 

Derdalium giganteum. 

Dentalium loeve. 



Pelecj'poda : — 

PanopcBa sulcata. 

Mactropsis Irailli. 

Mactra ovata. 

Tellina anyulata. 

Dosinia subrosea* 

Venericardia awamoaensis. 

Vulsella australis* 

Lithophagus truncaius.* 

Anornia alectus. 

Lima paleata.* 

Pecten polymorph ioides. 

Pseudamussiurn huUoni. 

Glycimeris globosa. 

Glycimeris traversi. 

Limofsis aurita. 

Limopsis insolita. 
Polyzoa : — 

Retepora. 

Flabellum sphenodeum. 

Flabellum circulars. 
Echinodermata : — 

Fragment apparently Hemipatar/us. 
Brachiopoda : — 

Rhynchonelln nigricans.* 

Terebratula concentrica. 

Magellania parki. 

TerebrateUa gnulteri. 



The organisms marked with an asterisk are now living on the adjacent coast. 

The total number of speciesf is 44 ; the number of recent species included in the list is 
12 : the percentage of recent species is therefore 27. Twenty-four of the species, or 54 per 
cent., have been foimd by Park in the Miocene rocks of Otago and Southland. There are 
important differences between the faimas recorded by him in the southern localities and that 
mentioned above. The most characteristic fossil found by him is Pseudamussiurn huttoni, 
a form that was represented by a single specimen in the WTiatatutu Subdivision collection. 
No specimens of CucullcBa were found. 1 but Glycimeris and Limopsis were extremelv 
abundant. 

It is possible that these differences may in part be explained by differences in station, 
but it seems more likely that a somewhat later period of deposition may be the correct explana- 
tion, for the Cucullceas in particular suggest an older fatma. 

On the other hand, the percentage of living species is no greater in this fauna than in 
the fauna of the various collections made in the southern districts. It has often been pointed 
out that too much insistence should not be laid on the proportion of living species, for a personal 



t Mollusca only. 

J As remarked on page 21, specimens of CucuUcea alta were discovered after Dr. ^Marshall's inspection. 



28 

equation of considerable magnitude is involved, especially wlion, as in this c-nse, nianj' of tlio 
organisms are represented by fragmentary remains. 

After a full consideration of these matters the writer is of opinion that the strata of the 
Whatatutu area should be refen-ed to the Upper Miocene. This o])inion is strengthened 
by the similarity between the fauna of this series and that of the Patagonian Mollasse, as 
described by Dr. Otto Wilckens. 

The natiire of the fossils indicates that climatic conditions prevailing at the time of the 
deposition of their sediments were almost identical with those that we now experience. There 
are no genera or species which have specially marked affinities with n\ollusca of warmer 
districts. Agaiii, the species of the different classes of animals represented do not possess 
the large or strong forms which usually characterize in some degree the fauna living in 
warmer climates. 

The fauna is distinctly a shallow- water type, in general relations similar to a fauna wliich 
might at the present time be found on the sea-floor at any depth less than 100 fatlionis. for 
the e.xtinct species are closely related to living forms. 

In previous geological descriptions of this district by Mr. McKay the rocks have been 
subdivided into various stratigraphical groups. These divisions were not based on paUvon- 
tological evidence obtained witliin the area now described, but upon stratigraphical and 
lithological correlations with rocks found some distance away on the coast-line. 

A CYetaceoiis age was assigned to some members of the series because of the occurrence 
of Inoceramus in strata near Waiapu, and because of the discovery of some remains of a sup- 
posed species of this genus in concretions in the bed of the Waipaoa Kiver. Although careful 
search was made for such fossils during the collecting of the fossils here described, none was 
found, nor was there any pala-ontological evidence in favour of a Cretaceous age for any of 
the rocks. 

It is also stated by Mr. McKay that the lowest bed of his Lower Miocene is a conglomerate 
of crystalline rocks. Within the Whatatutu Subdivision an outcrop of this conglomerate on the 
Waipaoa River opposite Waipaoa Station was carefully examined. The underlying clay- 
stones contain Limopsis auritin. and differ in no way from the claystoiies elsewhere. 

Lastly, the rocks at the oil-spring on Waitangi Hill are said to be of Cretaceous age. Here 
Limopsis insolita, Terebratella gaulteri, and Cahjptrcpa cahjptrceijormis were found. These 
are similar to fossils found elsewhere in the series. 

Boulders with Glydmeris and associated fossils were foxmd by McKay in the river-gravels 
in 187.'i. The occurrence of these was explained by him as derived from a series of rocks 
that was supposed to overlie the Cretaceous rocks of the area. The field-work has shown 
that rocks with abundant Glycitneris remains occur on a level with the floor of the Waingaromia 
Valley and no unconformity separates them from the lowest rocks of the district. 

It appears therefore that, in spite of previous contrary reports made when the country 
was less accessible and more difficult to traverse, no well-founded reason has yet been 
advanced to prevent the inclusion of the whole of this rock-series in the Upper Miocene. 

Structure. 

Intrnduclicn. 

It is well known that the sedimentary strata which constitute so much of the solid 
crust of the earth were laid down originally in an approximately horizontal position. These 
strata have been subjected to earth-movements, and during this process a departure from 
horizontality has in most cases taken place. This inclination is termed the " dip," and is 
measured in terras of its direction and its angle of inclination. Various structures are described 
in terms of the dip of the strata — for example, a " monocline " where the beds dip in a single 
direction ; an " anticline " where the beds are arched so as to incline away from one another, 
with the convexity of the arch upwards ; a " syncline " where the beds incline towards one 



24 

another, with the convexity of the arch downwards ; a " dome " when the beds inflined in 
all directions from a central point — that is, have a quaquaveraal dip.* 

The conditions generally accepted as essential for the accumulation of oil ir an area are 
(1) a sulficient supply of oil, (2) a porous leservoir rock in which it may be stored, and (3) an 
impervious cap rock which will prevent its escape. Conditions which favour its accumulation, 
but are not always essential, are (-1) gentle undulations of the strata, forming anticlinal arches 
or domes, (5) the complete saturation of the rocks with water, and its slow circulation under 
hydrostatic head or convection due to differences of temperature.f 

Conditions 4 and 5 above involve the anticlinal theory. The anticlinal theory of oil- 
accumulation assumes that the oil, being of lesser gravity, rises above the water present in 
porous rocks and collects at the highest possible points in upward folds, being there confined 
by impervious strata arching over the folds. The pressure of water, according to this theory, 
is considered as fundamentally necessary for the carrying-out of the process of accumula- 
tion in anticlines. I 

There are, however, some objections to the hydrostatic pressure assumed in this theory. 
The advocates for the theory of the volcanic origin of oil propose the view that the pressure 
produced by solfataric gases is the true reason of the migration of oil.§ The anticlinal theory 
has been found applicable to a large number of the oilfields of the world, || but has not yet 
proved to be of universal application. 

It is, however, a generally admitted fact that an anticlinal and especially a domal structure 
favours the accumulation of oil, and for this reason special attention has been devoted to 
the location of the anticlinal folds in this area. 

General Structure. 

The structural axes of the main anticlinal and synclinal folds of the subdivision are out- 
lined on the maps of the Waingaromia and Mangatu survey districts accompanying this report. 
The full lines represent the portions of the axes of which the positions have been ascertained 
from the stratification exhibited in the rock-exposures. The broken lines represent the pro- 
bable position of the continuation of these structural axes, as judged from the stratigraphy 
of rock-exposures situated perhaps at some distance from the axes, or from the position of 
structural axes in their \icinity. 

It will be seen from the maps that the structure is by no means a simple one, and that 
the area has been subjected to considerable and somewhat irregular folding. To map accu- 
rately the structure of such an area, a geological survey must be carried out with the utmost 
detail. Owing to the absence or obscure nature of the stratification of a large proportion 
of the rock-exposures, it is possible to learn the structure of certain portions of the area only 
by deduction from the result of an examination of the structure of the surrounding portions. 
Hence when the areas immediately adjoining the boundaries of the subdivision have been 
geologically examined, the true structure may in some cases prove to be slightly different 
from that represented. For this reason, to assume that the anticlinal folds will continue 
beyond the limits of the subdivision, trending in the same direction as that in which they 
reach these limits, might lead to serious error. As an example of this, the rocks exposed in 
the south-central area, in the Waipaoa and Waihora river-valleys, do not show stratification, 
so that the line representing the continuation of the Toromiro anticline is in this portion of 
the district a somewhat arbitrary one. 

* For further ex]ilanation of these and other terms used in this report the reader is referred to any one 
of the numerous text-books of geology — for example. Chamberlain and Salisbury, " Geology " (3 Parts) ; 
Dana, " Text-book of Geology " ; Geikie, '" Text-book of Geology " ; Le Coute. "' Elements of Geology." 

t '• Oilfields of Texas-Louisana Coastal Plain," by Hayes, C. W.. and Kennedy, W., U.S.G.S., 1903, 
Bulletin 212, p. 140. 

% " Geology and Resources of the Santa Maria Oil District, California," bv Arnold. R.. and Anderson, R., 
U.S.G.S., Bulletin, No. 322, p. 71. 

§ " Volcanic Origin of Oil," Coste, E. .Journal of Franklin Inst., 1904. vol. xv. pp. 443-34. 

II " Petroleum and its Products." Redwood, Boverton. Assisted by Holloway, G. T., 1st edition, 1896, 
vol. i, pp. 11 1 6 ; also 2nd edition. 1906, vol. i, ]). 112. See also references given in " Gieology and Resources 
of the Santa Maria Oil District. California," Bulletin No. 322, U.S.G.S., p. 71. 



25 

The folding in the eastern half of the area is fairly regular, the anticlinal and synclinal 
axes having a general north-oast and south-west trend, and being approximately parallel 
to one another. Only two exceptions occur — namely, the anticlines with a general north- 
west and south-east trend, which form domes with the Waitangi and Toromiro anticlines. 

The foldiiig in the western half of the area is decidedly irregular. The continuation of the 
Waitangi anticline, known as the Whcao anticline, takes place with a double bend forming 
an " S." To the upper loop of the " S " anticlinal axes converge from the west, the north- 
west, and the north. It is not clear from the limited area which has been examined whether 
this irregularity is due simply to one compressional folding, or to folding having taken place 
at two distinct- periods, with the pressure acting in different directions. 

Detailed Structure. 

The Pakarae anticline has a general north- and-soutli trend, and. as far as can be judged 
from the limited portion of its eastern slope examined, is in the form of a curve with its con- 
vexity towards the west. It is situated in the extreme eastern portion of the subdivision, 
in the vicinity of the confluence of the Rosebud Stream with its right branch A. The crest 
of the fold has been in part denuded by each of these streams and by the Whakauranga Stream, 
leaving exposed argillaceous sandstones containing calcareous concretions. On the eastern side 
the rocks are fossiliferous argillaceous sandstones interstratified with thin clavstones bands, 
showing an angle of dip increasing from IS'^ to 25° as the distance from the crest becomes greater. 

On the western side of the crest of this anticline the rocks consist of a deposit of fine- 
grained argillaceous sandstone, for the most part fossiliferous, occurring either alone or inter- 
bedded with daystone bands. The angles of dip vary from 10° up to 45°. The general strike 
of these beds over an area of some thirty square miles shows that a curvature corresponding 
to that on the crest of the fold occurs on this slope. 

The anticline, from the outcrops exposed in Branch B of the Rosebud Stream, plunges 
down towards the north, and. as will be seen from the above descrij)tion, has a tendency to 
be domal in arrangement. 

The Arakihi syncline has a total length within the subdivision of fourteen miles. Its 
geni^ral trend is north-north-east and south-south-west, but its actual course is decidedly 
sinuous. Its trough is moderately well marked for the northern eight miles of its length, 
but the structural line representing the southern si.x miles of its course is somewhat suppo- 
sitional. The synclinal axis enters the area about half a mile due west of the north-eastern 
corner of the subdivision. Its southern extremity is evidently in a synclinal basin which 
has its centre about the median point of the southern boundary of the Waingaromia Survey 
District. This synclinal basin has a radius of some three miles and a half. The rock which 
appears on the surface of its central portion is a fairly coarse fossiliferous sandstone wlii( li 
shows either indefinite stratification or none at all. The rocks surrounding this central 
portion are beds of fossiliferous argillaceous sandstone, which towards the outer edges of the 
basin have interstratified with them thin bands of daystone. The maximum dip is shown 
bv the beds on the circumference of the basin : those towards the centre dip at lower angles. 

The trough of the Arakihi syncline has many undulations. From Arakihi Peak it plunges 
downwards in a southerly direction, reaching its lowest limits in the centre of the synclinal 
basin. From the same peak it plunges slightly in its northerly extension, rising again in 
the vicinity of Paraheka Peak, with again a slight plunge downwards in its extreme northern 
portion. 

The Paraheka anticline has a length of slightly over two miles. Its general trend is 
north-north-east and south-south-west. The crest of this fold has a slightly sinuous course, 
but throughout its length is almost parallel to that portion of the trough of the Arakihi syncline 
which lies adjacent to it. The most northerly limit of this anticline is at a distance of half a 
mile north of Paraheka Peak. It noses out at each end at the points of junction of the Para- 
riki and Arakihi synclincs. 



26 

Tlic iinticliiie is apparently alow one. The beds on its crest consist of moderately coarse 
sandstones, interstratified with like bands containing abundant fossil shells, underlain by 
fossiliferous argillaceous sandstone interbedded with claystone. The sequence is similar to that 
occurring in the trough of the Arakihi syncline about this point, with the exception that among 
the highest beds exposed on the crest of the anticline occur indurated sandstone bands con- 
taining abundance of shells. 

The Parariki syncline lies to the west of the Paraheka anticline, with its trough approxi- 
mately parallel to the crest of the latter. At both its northern and southern extremities it 
terminates at the Arakihi syncline, one extremity being about one mile north and the other 
about three miles slightly west of south from Paraheka Peak. Its total length is four miles. 

The southern portion of this syncline is apparently shallow and contracted. At no great 
depth lies the chalky limestone of the Lower Whatatutu Series. The beds of fossiliferous 
argillaceous sandstone and claystone that overlie the limestone have a somewhat steep dip 
at an angle of about 20° to 30° on eacTi side of the trough. Farther north the trough apparently 
plunges downward slightly and becomes less contracted, the angle of dip being about 10°. 
The continuation of the syncline is across the left branch of the Paraheka Stream and along the 
westward slope of the main divide, imtil it meets again the Arakihi syncline. 

The Tuarua anticline has a length of about one mile within the subdi\nsion. Its crest is 
parallel to the northern portion of the trough of the Arakihi syncline, and has a north-north- 
east and south-south-west trend. The beds on its south-eastern flank are of argillaceous 
sandstone and claystone, with occasionally thin bands of sandstone. The beds dip steeply 
(angle 25°) down to the trough of the Arakihi syncline. The beds on the north-western flank 
are of a similar nature, but dip at a much lower angle (10° to 15°) towards the trough of the 
Omega syncline. 

The Omega sjnicline has a similar length, and is parallel to the Tuarua anticline. The 
beds that form the southern portion of the trough of this syncUne consist of argillaceous sand- 
stone and claystone dipping on each side at an angle of 15°. The trough plunges do\vnwards 
slightly towards the north, and shows fossiliferous indurated sandstone bands and shelly 
conglomerate bands interstratified •w'ith similar beds to those occurring in the southern 
portion. 

The Toromiro anticHne is one of the main anticlinal folds of the area. It extends through- 
out the subdivision from the northern to the southern boundary with a general north-east and 
south-west trend. The ridge separating the Waingaromia and Waihora valleys roughly re- 
presents the position of its crest in the southern half of its length. The northern half of the 
fold has been dissected transversely by the Makahakaha-Ngarara and Parariki streams and 
their branches, and the crest of this portion of the fold is situated on about a median line between 
the Waingaromia River bed and the main divide. 

The main Toromiro anticline is crossed by a smaller one, some three miles in length, 
with a trend north-west and south-east, or transverse to the direction of the main fold. Both 
anticlines plimge downwards in the direction of their lengths from the point of crossing, giving 
rise to a domal arrangement of beds, the centre point of which is situated about a mile and a 
half slightly west of north from Hokoroa homestead. 

The rocks exposed on the summit of this dome consist of fine-grained argillaceous sand- 
stone, interbedded with claystone and sandstone, and at a short distance down the eastern 
slope dip at an angle of 15°. At an elevation of 400 ft., below the crest of the ridge, chalky 
hmestone is exposed in the Makahakaha-Ngarara Stream, overlain by beds of sandstone and 
claystone, dipping at an angle of 25°, similar to those on the crest of the ridge. In the Makaha- 
kaha Stream bed, on the south-eastern slopes of the dome, are exposed claystones with cal- 
careous concretions. The same beds occur on the south-west slopes of the dome, and the 
occasional outcrops of interbedded sandstones and claystones on the north-west plunge of 
the smaller anticline evidently overUe them. The rocks exposed in the branches of the Rau- 
mate Stream are similar to the above — namely, claystones with calcareous concretions over- 



'27 

lain by interbedded claystones and argillaceous sandstones. Here the latter beds show a dip 
at an angle of from 30° to 35°. 

On the northern plunge of the Toromiro anticline the rocks exposed are argillaceous 
sandstones and claystones dipping at an angle of 15° to 25°. In the Parariki Stream, above 
its junction with the Paraheka Stream, argillaceous sandstones containing concretions have been 
exposed on the crest of the fold, and are overlain on the western slope by argillaceous sand- 
stone and daystone dipping at an angle of 15°. 

The downward plunge from the dome on the Toromiro anticline in a south-easterly direc- 
tion is followed by a slight rise in the vicinity of Toromiro Hill. Here are exposed, in the beds 
of the Te Hina Hina and Toromiro streams, claystones and argillaceous sandstones containing 
concretions. F:irther south the same beds occur along the crest of the ridge separating the 
Waihora and Waingaromia rivers, and, on its eastern and western slopes, in the beds of the 
tributaries of these rivers. At the head of the Hauomatuku Stream, where the anticline appears 
to be again plunging downward, these beds are overlain by sandstone containing numerous 
fossil shells. 

The Waingaromia syncline extends across the subdivision, with a general north-east and 
south-west trend. It is approximately parallel to the Toromiro anticline, but its course is 
a great deal more sinuous. The Waingaromia River has its bed practically in the trough 
of this syncline. In its northern portion the syncline has a plunge downwards towards the 
north, and beds of daystone and fossiliferous sandstone, in some cases containing shelly con- 
glomerate bands, form the trough, and dip at low angles (maximum 10°). These beds on 
the crests of the spurs are covered by the coarse sandstone that is considered to be the highest 
member of the Whatatutu Series. Farther south, where the Waingaromia River bed follows 
the trough of the syncline, claystones and argillaceous sandstones containing concretions 
are exposed with fossiliferous claystones overlying. The same beds are exposed in Tawa 
Stream. In its south-westerly extension from this stream the exposures are for the main 
part of claystones. The southern portion of the syncline appears to have a slight downward 
plunge towards the south. 

The Waitangi anticline is the second of the principal anticlines which occur in this sub- 
division. Its general trend is north-east and south-west. In the main this fold is parallel 
to the Toromiro anticline, but its northern portion swings round from north-east to north 
and its southern portion from south-west to slightly north of west. The crest of tiiis anti- 
cline occupies the ridge separating the head-waters of the Waipaoa and Waingaromia rivers at its 
northern extremity. As it passes south it crosses the Tawa and Waitangi streams in theii 
middle courses, pas.ses through Waitangi Hill and down the valley of the Mangataikapua 
Stream, then turns slightly north of west, and passes across the Waipaoa River and through 
the ridge on its western side into the Mangatu Valley, where a dome has been formed by its 
junction with the Mangatu anticline. This dome will be described in connection with the latter 
fold. 

The Waitangi antichne is crossed by a small anticline, and thus a dumal arrangement 
of beds at the crossing-point results. The summit of this dome is about half a mile west of 
Trigonometrical Station 138. The smaller anticline has the form of a curve with its con- 
vexity towards the south-west, and extends from the Makara Stream through Waitangi Hill 
to the Waingaromia River, having a general trend north-east and south-west, or about trans- 
verse to the trend of the main fold. Not far from the summit of this dome occur the well- 
known oil-seepages of Waitangi Hill, and at or very near the actual summit is situated the 
borehole now being sunk by the Gisborne Petroleum Company. 

On the summit of the dome the rocks that are exposed in the stream-beds, &c., consist 
of claystones and argillaceous sandstones, with, in some cases, interbedded indurated sand- 
stone bands. These overlie the glauconitic-sandstone beds, portions of which are exposed 
in the vicijiity of the main oil-spring probably to a depth of 5(X) ft. On the southern slopes 
fossiliferous sandstones, fossiliferous claystones, and claystones containing concretions over- 



28 

lie tlie gliUKoiiitic-sandstone beds. Un the western and south-western slopes the glauconitic 
sandstones overlie beds of chalky limestone. Outcrops of tlie latter beds occur also on the 
northern slopes of the dome, and are overlain by claystones and argillaceous sandstones. 
Such beds as show stratification near the summit of the dome dijj at high angles, from 30° up 
to 60°. 

The outcrops exposed in the Waitangi Stream bed are fossiliferous argillaceous sandstones, 
dipping at an angle of from 30° to -45°, the structure apparently being indicative of a steep 
plunge of tlie anticline from the dome towards the north-east. 

The outcrops which form the crest of the Waitangi anticline, still farther north, are of 
fossiliferous argillaceous sandstone, with a dip of about 10°. 

The denuded crest of the fold as exposed in the valley of the Mangataikapua Stream 
shows chalky limestone overlain in places by glauconitic sandstone. Where dip is shown 
in this valley it is at high angles, up to 75°. The north-western flank shows fossiliferous 
argillaceous sandstones interbedded with claystones dipping at an angle of 10°. The south- 
eastern flank shows claystones with concretions, overlain by claystones and argillaceous sand- 
stones dipping at angles of 4:0° to 60°. Where the anticline crosses the Waipaoa Valley chalky 
limestone is exposed on the southern flank, overlain by argillaceous sandstone and claystone 
dipping at angles from .30° to 50°, capped by a bed of limestone. In the Mangatu Valley 
chalky limestone is exposed in the river-bed, and glauconitic sandstone on the eastern slope 
of the ridge to the north of this river. The southern flank of the fold shows argillaceous sand- 
stone and claystone dipping at angles of from 20° to 35°. 

The anticline which crosses the Waitangi anticline at Waitangi Hill shows fossiliferous 
sandstones dipping at angles from 30° to 55° on the north-eastern side of the dome, and clay- 
stones interbedded with thin sandstone bands dipping at an angle of 20° on the eastern side. 

Between the crests of the Waitangi and the Mangatu anticUnes is included an area roughly 
triangular in shape, with the base of the triangle lying towards the north. The structure of this 
area is that of a syncline, which has, in its general downward slope from the crest of the Wai- 
tangi anticline to the trough of the Waipaoa syncline, two minor undulations represented 
by low anticlines. One of these — namely, that crossing the Waitangi anticline at Waitangi 
Hill — has already been described. The second, named the Makara anticline, lies a short 
distance westward, and can be best dealt with after a description of the Waipaoa syncline 
has been given. 

The Waipaoa syncline has a length of some five miles. Its trough has a general north 
and south trend, and appears to have formed originally a natural watercourse for that por- 
tion of the Waipaoa River which lies to the northward of the village of Whatatutu, since 
the present river-bed is almost parallel to it, and is situated but a short distance to the west- 
ward. The length of the slope from this trough to the crest of the Mangatu anticline is much 
less than that from the crest of the Waitangi anticline, but the latter slope, as already stated, 
is undulating. 

There is a decided downward plunge in a northerly direction from the southern extremity 
of this trough, and probably also a downward plunge in a southerly direction from its northern 
extremity, so that in the central portion higher beds of the Whatatutu Series are exposed 
than at the extremities. In that portion where the trough rises to the northern flank of the 
Waitangi anticline the beds exposed are chalky limestone and glauconitic sandstone. Farther 
northward fossiliferous argillaceous sandstones, interbedded mth claystones, are seen in the 
Waipaoa River bed, and, apparently overlying these rocks, fossiliferous argillaceous sand- 
stones of coarser texture than the first named, as exposed on the Mangatu Road. The dip 
of the strata exposed in the Waipaoa River beds is at a very low angle. The maximum is 10°, 
but in a great number of the exposures the beds are almost horizontal. On the Mangatu 
Road, however, the dip is at an angle of about 15°. Still farther northward, at and above the 
Ruahine Stream, the beds on the eastern slope to the trough, as exposed in the Waipaoa River, 
contain indurated sandstone bands, shelly conglomerate bands, and conglomerate bands 



29 

(pebbles mostly of igneous origin) associated with cliiystone and fossilifeious argillaceous 
sandstone, and have in some cases an angle of dip as high as 45", Init in general of about 15° to 
20"". The beds on the western slope, as exposed on the Mangatu-Waipaua Stock-ti'ack, are 
of fossiliferous argillaceous sandstone, in places containing indurated bands. Their angle of dij) 
is about 20°. 

The rocks forming the extreme northern portion, as exposed in Homestead Stream, are 
claystones and argillaceous standstones which have apparently been lecently shifted from 
their original position. They exhibit a streaky and laminated appearance. Similar rocks, 
also much disturbed, are exposed in the Weraroa Stream. 

The Makara anticline lies to the eastward of the Waipaoa syncline. Its crest has a general 
north-and-south trend, and its course shows the same curves as, and is approximatelv 
parallel to, the trough of the Waipaoa syncline. It branches off the AVaitangi anticline from 
about the trigonometrical station marked /|v on the map of Mangatu Suivey District, and 
has been dissected by the left branches of the Waipaoa River northward from this point, and 
finally by the main river near its point of confluence with Homestead Stream. 

The anticline, which is of moderate height, plunges downward from Trigonometrical 
Station A in a iu)rthcrly direction, but ajipears to rise again in the vicinity of its dissection 
by the \\ aipaoa River. 

Throughout its length the rocks forming the crest of the fold are .similar to those forming 
its flanks. In the southern portion the beds exposed arc of fossilferoiis argillaceous sand- 
stone and daystone, dipping at angles of from 5' to 10" on the western Hank, but in the one 
outcrop exposed on the eastern flank they dip at an angle of about 60°. In the Pukekuri 
Stream similar beds occur, but here have indurated sandstone bands interbeddcd. The angle 
of dip is about 5°. In the bed of the Makara Stream outcrops of fossiliferous argillaceous 
sandstone and daystone occur, dipping on each flank of the fold at low angles (maximum 8°). 
With the exception of outcrops in the bed of the Weraroa Stieam, at a point half a mile above 
the northern boundary of the subdivision, which show an anticlinal arrangement, there is no 
stratified outcrop to prove that the Makara anticline continues northwards farther than 
half a mile from the Makara Stream. 

This continuation would, however, appear actually to occur, for four reasons : (I.) There 
is evidence of a synclinal arrangement of beds trending north and south, in the bed of the 
Mangaorango Stream about three-quarters of a mile above its mouth. (2.) Beds of conglo- 
merate occur in Conglomerate Stream and in Atarau Stream. The contents of these beds 
are identical, and it is probable that they belong to the same stratum. Since in each case 
the beds dip to the south-west, the folding suggested would account for the occurrence of 
two portions of the same stratum in these two localities. (.3.) The Weraroa fault, described 
on page 33, would account for the disappearance of the conglomerate bands on the eastern 
flank of the anticline. (4.) The distance between these two outcrops of conglomerate is three 
miles, and, since the beds exposed throughout this distance dip at angles averaging 20°, the 
absence of folding would necessitate that after the bed of conglomerate in Atarau Stream 
had been laid down it was covered by a thickness not less than 5,(KK) ft. of beds of argillaceous 
sandstone and daystone before the formation of a bed of conglomerate almost exactly similar 
to the first. 

The Mangatu anticline has a general north-and-south trend. It is difficult to locate the 
actual position of the crest of this fold owing to the fact that the rocks exposed throughout 
the greater portion of its length do not show stratification. The bed of the Mangatu River 
either follows the crest of this fold or has cut down the eastern flank. 

At its southern extremity the Mangatu anticline joins the Waitangi anticline, giving 
rise to a domal arrangement about half a mile north of the mouth of the Mangamaia Stream. 

The rof-ks exposed on the crest of this dome are chalky limestones, and the same stratum 
forms the crest of the fold along its northerly extension. On the southward slopes are exposed 
beds of argillaceous sandstone, with occasional bands of indurated sandstone, dipping at an 
angle of about 20° 



30 

The eastern flank shows argillaceous sandstones dipping at an angle of 15", as exposed 
on the Mangatu Road. Farther north in the head-water valley of the Otamaharama Stream 
the chalky limestones aic directly overlain by beds of fossiliferous argillaceous sandstone 
dipping at an angle of 15 . In the head-water valley of Te Hua Stream fossiliferous argillaceous 
sandstones interbedded with fine-grained sandstones dip at an angle of 10°. These beds 
overlie the chalky limestones exposed in the stream-bed towards the mouth. Farther to 
the north the chalky limestone is overlain by laminated claystones similar to those of Home- 
stead and Weraroa streams. 

The western slope of the Mangatu anticline as far as the ilanjiatahu Stream shows onlv 
chalky limestone rocks. In the bed of this stream clay-shale underlies the chalky limestone, 
which in the headwater valley of the Aotea Roa Stream and other right-hand branches of 
the Mangatahu is overlain by glauconitic sandstone. 

From the outcropping of clay-shales in the northern portion of this fold it would appear 
that it is rising towards the north. 

The Wairere syncline is a shallow structural depression between the Mangatu and Manga- 
papa anticlines. Its general trend is north-north-west and south-south-east. The actual 
position of the trough of the syncline is difficult to locate, owing to the fact that the rocks 
exposed throughout its length are in general but poorly stratified. The trough plunges do%\Ti- 
wards slightly from each extremity towards its central portion. 

The rocks exposed on the slopes of the trough are glauconitic sandstones, which overlie 
chalkv limestone exposed higher up the slopes towards the crest of the anticline. On the 
flank, sloping down towards the north-east, glauconitic sandstones with an angle of dip from 
20° to 40° are exposed in the bed of the Mangamaia Stream and on the northern portion of 
Mangahaumia Track ; while near the trough exposed in the Makerewau Stream they dip at 
an angle of 45°. On Trigonometrical Station M 1, and for some distance on either direction 
along the ridge on which it is situated, glauconitic sandstone showing no stratification is 
exposed. 

On the flank which slopes towards the south-west glauconitic sandstone with indeter- 
minate stratification is exposed in the right branches of the Mangatahu Stream and on the 
ridge separating this stream from the Makerewau. 

The Mangapapa anticline has a general north-west and south-east trend. The crest of this 
fold is represented in its northern portion by the spur separating Matmgahaumia and Manga- 
papa streams, and has been dissected by the latter stream. Beyond this point it constitutes 
roughly the water-divide between the Mangapapa and Mangamaia streams vmtil in the vicinity 
of subtrigonometrical station A it coalesces with the Wheao anticline, which has an S-shaped 
course, and forms a continuation of the Waitangi anticline. 

The rocks exposed on the crest of this fold are mainly limestone, those on the crests of the 
ridges resembling the chalky limestones, whilst the lower portions, as in the gorge of the Manga- 
papa above its confluence with the Mangahatmiia, have a somewhat shaly character. At 
its western extremity the anticlinal crest exhibits coarse sandstone beds. 

The north-eastern flank of the Mangapapa anticline shows chalky limestone, overlying 
beds of limestone with shaly appearance that dip at angles of 20° to 30°. On the south-western 
flank limestone rubble is shown in Mangahaumia and Big Slip streams, and just below their 
confluence with the Mangapapa chalky limestone overlying shaly limestone occurs. Lower 
down the bed of the Mangapapa the stream passes through a limestone gorge, while below 
this are exposed claystones of indefinite structure containing many calcite veinlets and argil- 
laceous sandstone in regular bands dipping at an angle of 15°. 

The Mangahaumia syncline, which occurs between the Wheao and the Mangapapa anti- 
clines, evidently has its trough nearer to the crest of the latter than to that of the former. 
The general trend of its trough is north-west and south-east. The Big Slip fault, striking 
west-north-west and east-south-east (see p. 33 and section on map of Mangatu Survey 
District), has considerably altered the north-eastern slope, and the absence of undisturbed 



31 

outcrops on this slope precludes the possibility of accurately locating the position of its 
trough. 

On the north-western slope down from the crest of the Wheao anticline, however, the 
constant dip of the l)eds towards the north-east and north-north-east proves that the tronjih 
must be located to the north-east of the Urukokomoku Stream bed. 

The beds in the vicinity of the trough, as exposed in the valley of the Urukokomoku, dip in 
general at an angle of about 10°. At the head-waters they consist of calcareous sandstones 
covered by coarse sandstones. In the middle course of the Urukokomoku thev consist of 
argillaceous sandstones with which are interbeddcd bands of conglomerate containing igneous 
boulders (see p. 18). In the lower middle course they coflsist of argillaceous sandstone 
with some daystone bands. At a point about two miles from the mouth of the stream the 
rocks in the bed show a sj'nclinal arrangement, and this is probably the western extremity 
of the syncline. 

The Wheao anticline is perhaps the best-defined fold in the area. Its crest has a general 
east and west trend for the greater portion of its length. Towards the east its trend changes 
to north-east, to north, to north-west, again north, and finally east-north-east to the donu^ 
formed by the union of the Mangatu and Waitangi anticlines. Its general course in the eastern 
portion is thus that of an S, the lower loop of which is considerably the larger. 

The crest of the fold, in the western portion, has been cut through by the Ngamangatawa 
Stream, which shows in its bed claystones and argillaceous sandstones dipping to the north 
at 15° and to tiie south at 30°. Farther east the rocks are moderately coarse sandstone con- 
taining glauconitic grains, as exposed in the Devil's Elbow Stream. W here the crest of the 
fold has been denuded by the Wheao Stream the beds are of argillaceous sandstone dijiping 
to the north-west and to the south-east at an angle of 15°. On the ridge separating the Wheao 
and Urukokomoku streams, sandstone outcrops, while in the Urukokomoku Stream bed 
argillaceous sandstones dip to the west and to the east at angles of from 5° to 15°. In the 
Mangapapa Stream bed argillaceous sandstones dipping to the south-east and west at an 
angle of about 10° occur. In the vicinity of Subtrigonometrical Station A, and from this point 
to the Mangatu-Waitangi dome, chalky limestones form the rocks on the crest of the fold. 

At the eastern end of the northern flank the coarse sandstones overlie argillaceous sand- 
stones and claystones. The angle of dip of these beds is as high as 60°, but flattens out to about 
10°, as shown in exposures in the Urukokomoku Stream. Similar beds occur on the ridge 
separating the \\'heao and Urukokomoku valleys. 

On the flank sloping towards the south the beds, as exposed in the Waikohu River bed, 
consist of argillaceous sandstones and claystones. which have an increasing angle of dip from 
15° to 45° as far as the mouth of the Devil's Ell)ow Stream. Between this point and Sub- 
trigonometrical Station Peg IV the dip is at angles of from 30° to 45°. 

In the Mangamaia Stream bed argillaceous sandstone and claystone beds occur, dipping 
to the eastward and south-eastward at angles from 20° to 35°, to a point ;ibout half a mile 
distant from the mouth of the stream, where the dip changes to the south at angles from 
20° to 25°, and finallv to the south-west at 45°, thus representing the changes in the trend 
of the crest of the fold. 

There is evidence of a minor anticlinal fold existing between subtrigonometrical station 2 
and the Poututu accommodation-house. The fold, which is not sufficiently definite to be 
marked on the map, appears to strike in an east-and-west direction. 

The structure of an area of some eleven square miles lying to the westward of the Whata- 
tutu-Puha Road has not been definitely ascertained. This area is triangular in shape, with 
a base of some six miles in length, corresponding in position with the southern boundary 
of the subdivision. Within this area the rock-exposures consist of claystones not showing 
stratification overlain by beds of pumiceous material. It seems possible that these clay- 
stones are exposed on the crest of a low anticline with a general north-north-east and south- 
south-west trend ; but they may also be forming a monochne with a very low inclination 



32 

towards the trough of the Waingaromia syncline. A geological survey of that portion of 
t he Waikohu Survey District adjoining this area would no doubt afford much useful informa- 
tion concerning this point. 

The Waipaoa Series. 

The exposures of the beds of the Waipaoa Series are mainly confined to the valley of the 
Waipaoa River. Here they consist of loosely compacted pumiceous material, and overlie 
the claystones that form, for the most part, the rocks of that part of the Waipaoa Valley 
south of the village of Whatatutu. The pumice deposits were found covering the crests 
of the spurs in the vicinity of the Otuhira, Omanuporoaki, and Maugakino streams ; on the 
western side of the Waipaoa River bed ; on the crest of the ridge on which Trigonometrical 
Station 145 is situated, and on the spin's which run down therefi'om to the eastern bank of 
the Waipaoa River. These deposits attain a maximum elevation of about 1,400 ft. 

At Tapuihikitea, pumice deposits, in some cases attaining a thickness of 20 ft., overlie 
the denuded edges of claystone rocks, and are covered above by the gravels which form the 
surface of the 200 ft. high-level terraces. Outcrops were also observed in the spm' separating 
the Ratahi and Hinakiwawahia streams, and on the crest of the main divide at the head of 
the right branches of the Ratahi Stream. On the crest of the spur on the north side of Tawa 
Stream outcrops of the beds of this series were also examined. 

All of these outcrops consist of a loosely consolidated pumiceous deposit, which shows but 
little sign of having been laid down in water. 

Exposures on the Te Karaka - Motu Road in the vicinity of the Ngamangatawa Stream 
crossing ; in the Waikohu River bed, a short distance below Matawai homestead ; in the 
head-water branch of the Mangarara Stream ; and boulders obtained on the left-hand bank 
of the Waingaromia River about four miles above Waitangi homestead, are more consolidated, 
and appear to have been deposited under water. The microscopic examination of a rock- 
section cut from a specimen obtained from the first of these exposures showed a few specimens 
of Foraminifera. It therefore appears that the rock was laid down under the sea. The general 
angular shape of the constituents points to the fact that they were not assorted by wave-action 
to any great extent. 

Loosely Consolidated and Unconsolidated Debris. 
Gravels, pebbles, and finer debris derived from the denudation and decomposition of 
the rocks of the area form the gravel-beds and flood-plains of the watercourses within the 
subdivision. The low-level and high-level terraces are covered by a layer of this material 
averaging about 10 ft. in thickness. It is certain that the gravels, &c., forming the upper 
portion of the low-level terraces and the 200 ft. high-level terraces are of younger age than 
the beds of the Waipaoa Series. Those forming the covering of the 200 ft. high-level terrace 
are of yomiger age than the beds of the Waipaoa Series. Those forming the covering of the 
400 ft. high-level terrace may, however, be older, since in no case was a pvunice deposit observed 
overlying them. On the other hand, no pumice was found underlying them, so that this point 
must for the present remain undecided. 

Faults. 
The rocks occuiTing wathin the subdivision are in general of a friable nature, and sufEei 
considerably from surface erosion and decomposition, as before stated. They are also subject 
to creeps, and slumps or land-slides, so that for the most part the surface indications of faulting, 
such as fault-scarps, slickensided surfaces, &c., have been obUterated. Moreover, the beds 
of the Whatatutu Series, with the exception of the conglomerate bands, have not cha- 
racteristics sufficiently distinctive to allow" of the recognition of any particular stratum in 
different localities, and this, combined with the fact that portions of the series exhibit no 
stratification, renders the location of faults somewhat difficult. Such faults as have been 



2h iiiri'mpnny BtiUnfin, N^9, mtctfof^itu Suhdivisiofi,.liaukiifHfircvJ)ivistOTv.tto-nkesMayLafuJ Uisfrict 




RoaAs shown, thibs 

Trig. Stations n ■.. 

ConghomeraUBonils ,, . . 

/^^§^A:^ Ea:ti.nct GasVe^ts _ 

ProposfdSorm^ Sites,. „_ 

OiX Sprvx^S tr- 

Outcrops wUh observed, striko if dtp A 




Compiled from. data. oiCatntd from Ote 
LandsDepjrcment, and additional survtys 

by J.RAdams.ofthc Geoia^ical Su-rvi^ 



GEOLOGICAL MAP OF 

r 



- Scale of Chains - 



UPPER AaiClaystone and arg.Dacaous 

MIOCENE \ 1^" * ""*' "^ . . ii„^,„,._ 
'■"Claystone and orgjflaceous 

erale, fossiliferoua a.fiillaceo 
SondEtone, coarse tandBton, 
Ws.paoo Beda:- 




PL(OCENE(?)jp^'J^^^'°^j 



PLEISTOCENE 1 Gravels, Sands I high '»«' terracea.L 
AND RECENT land muds (low L 



fllfll If. ||. I. 

r H JJiULii U J 



Section on Line B - C 




33 

indicated, though perhaps extending to some depth, represent generally comparatively slight 
dislocations, parallel to the strike, produced during the folding of the beds. 

The Waitangi Fault. — A fault has probably taken place slightly to the south-east of the 
Waitangi anticline. Evidences of this fault are to be seen from the oil-springs at Waitangi 
Hill to the Minerva borehole. 

The oil which shows on the surface of the pools at Waitangi Hill is evidently rising up 
a break or fault-plane with sufficient depth to penetrate the oil zone at this point. In the bed 
of the Mangataikapua Stream the chalky limestones exposed have, in the vicinity of the sup- 
posed fault-line, a crushed and slickensided appearance. The small left-hand branches of the 
Mangataikapua show boulders of crushed and slickensided material, and in Branch G of the 
same stream the much-broken country exhibits the evidences of faulting in slickensided sur- 
faces to a marked degree. On the supposed line of this fault there is a depression of the crest 
of the ridge separating the Waipaoa River and the Mangataikapua Stream, with Trigono- 
metrical Station A (Saxby Hill) on the south side at a lower elevation than the continuation 
of the ridge northwards. On the left bank of the Waipaoa River, in the vicinity of the Minerva 
borehole, the argillaceous sandstone and claystones have a crushed appearance. From the 
information available as to the nature of the rocks passed through in the Minerva borehole, 
they appear to have been much disturbed, as should be the case if the supposed continua- 
tion of the Waitangi fault to this point is correct. This fault appears to have a relative down- 
throw to the southward, for the outcrops exposed at Waitangi Hill and on the right bank of 
the Mangataikapua Stream show that on the crest of the Waitangi anticline the chalky lime- 
stone is directly overlain by glauconitic sandstone, but in the vicinity of the fault-line in the 
Mangataikapua Valley and on the left bank of the Waipaoa River the chalky limestone is 
directly overlain by argillaceous sandstones and claystones, with the apparent elimination 
of the glauconitic-sandstone beds. 

The Big Slip Fault. — The trend of this fault, as indicated on the map of the Mangatu 
Survey District, is about north-west and south-east. The evidences for its existence are 
a fault-scarp exhibited on the south side of Little Mangahauuia, the disturbed nature of 
the lieds in the Big Slip and Mangapapa streams, and the extremely steep slope on the 
southem side of the ridge separating the Mangapapa and Mangamaia streams. 

The Raukumara Range from Trigonometrical Station M 4 in a south-westerly direction 
has an average height of over 3.fi00 ft. until Little Mangahaunia is reached. On the south 
side of this peak is a scarp with an angle of inclination of 40°. The continuation of the range 
southwards has an elevation of some 1,000 ft. less than the summit of Little Mangahaunia. 

In Big Slip Stream there are no rocks to be seen in situ, all being covered with detritus 
from the continual slumping of material from Little Mangahaunia. In the Mangapapa Stream, 
below Mangapapa homestead, the beds are very much disturbed, in some cases having a crushed 
appearance. Below the limestone gorge, due south of Tahumara homestead, the formations 
are regular, and do not appear to have been affected by any fault. 

The southern slope from the crest of the spur separating the Mangamaia and Manga- 
papa streams is exceedingly steep, the angle of inclination being about 40°, and probably 
represents a fault-scarp. It would appear that in connection with this fault a fairly large 
mass of material, now forming the divide between the Urukokomoku and Mangapapa streams, 
has been thrust towards the south. As evidence of this supposition, the chalky limestone 
forming the main mass of the ridge overlies or abuts against argillaceous sandstones and clay- 
stones (higher in A\Tiatatutu Series : See table of formations, p. 12) dipping to the north- 
ward. Also this chalky limestone is similar to that fomiing the ridge separating the lower 
portions of the Mangamaia and Mangapapa streams, and in the latter case is at 700 ft. lower 
elevation. 

The Weraroa Fault has a trend slightly west of north and east of south. The evidences 
of this fault are the disturbed state of the strata in the vicinity of the mouth of the Weraroa 
Stream and in the Waipaoa River bed, the gas- vents on the ridge to the north of the Weraroa 
Stream and the extinct gas-vent in the Waipaoa River bed. 

3— Whatatutu. 



34 

At the mouth of the Weraroa Stream the I)eds are dipping at all angles, and the rocks 
composing them have a crushed and altered appearance. In the Waipaoa River bed the same 
description applies. An outcrop of claystone much shattered and altered, with a base some 
3 chains in diameter, stands up to a height of about 20 ft. above the river-level on the southern 
side at the mouth of the Mangaorango Stream. At the mouth of the Weraroa Stream the 
Waipaoa River bed is some 7 chains in width, and as far as the mouth of the Mangaorango 
Stream is considerably wider than the lower portion, a point which may have some significance. 

The gas-vents on the spur to the north of the Weraroa Stream have a general north- 
and-south aUgnraent, while a gas-vent, now covered by a slip, occurs in the Waipaoa river- 
bed about -40 chains above the mouth of the Mangaorango Stream (see map of Mangatu 
Survey District). 

The presence of this fault would account for the absence of outcrops of conglomerate 
on the western sloj)e of the Makara anticline (see p. 29). 

The northern portion of the course of the Mangatu River may have been determined to 
some extent by a fault with a north-and-soutli trend. The outcrops in the bed of this river 
are mainly of chalky limestone, and in some cases have a crushed appearance. 

Small local faults are of very frequent occurrence, and are very well shown on the cliff- 
faces of the gorges of the main Waipaoa River, and in other river-beds. 



35 



CHAPTER III. 



ECONOMIC GEOLOGY. 



Page 

Petroleum . . 35 

Origin of Petioleuni . . . . 35 

(1.) Theory of Inorganic Origin .. 35 

(2.) Tlieory of Organic Origin . . 35 
Petroleum-indications — 

(1.) Oil .. .. .. ..30 

Occurrences within the Sub- 
division . . . . . . 30 

Occurrences without the Sub- 
division . . . . 37 

Analyses of the Oil . . . . 37 

(2.) Gas . . . . 39 

General Occurrence . . . . 39 

Occurrences within and near the 

Subdivision . . . . 39 



Petroleum — continued. 

Probable Oil Zone 

Sites for Boreholes 
Material for Macadamising Purposes 

Conglomerate 

Burnt Pa])a 
Materials for Cemeat-making, &c. 

Limestone 

Clays 
Gold 
Coal 
Mineral Spring 



Page 

40 
40 
42 
43 
43 
44 
44 
45 
45 
46 
46 



Petroleum. 

The number of purposes for which petroleum is used in the world to-day and the still- 
increasing demand for it as a fuel places it in the first rank of economic minerals. Deposits 
containing petroleum are of widespread geographical distribution, and range geologically 
from Silurian to Quaternary times. 

Traces of petroleum have been found in igneous rocks — for example, in basalt, melaphyre, 
and granite ; but as an economic product it is obtained exclusively from rocks of sedimentary 
origin. Beds of porous character, such as sandstone, conglomerate, and crinoidal limestone, 
form the most suitable reservoirs for both oil and "as.* 



Ori(/in uj Petroleum. 

The origin of petroleum is a much-debated question that is as yet by no means settled. 
Two main theories have been propounded to account for its occurrence, brief outlines of which 
are here appended : — 

(1.) Theory o/ Inorganic Origin. — This theory depends on the fact that the action of acids 
and steam or water-vapour on acetylides and carbides of the metals produces such gases as 
acetylene, methane, ethylene, and hydrogen. In some instances, as when manganiferous iron 
rich in chemically combined carbon is acted on by acids, or when carbide of uranium is acted 
on by water, a residue of solid and liquid hydrocarbons is obtained. 

There is no direct evidence to prove that the conditions required by this theory exist 
within the earth's crust. 

(2.) Theory of Organic Origin. — Geologists are generally agreed that it is true of a large 
number of deposits that petroleum is indigenous to the strata in which it is found, or is derived 
from closely subjacent sedimentary strata.! The petroleum contained in these strata is 
held by some authorities to have been derived from the decomposition of animal matter, while 
others hold that it has been derived from the decomposition of vegetable matter. 

The theory of organic origin is probably the correct one, and with regard to this 
Sir Boverton Kedwood, a prominent authority, says, " Probably, on the whole, the Hofer- 
Engler views (that the petroleum is derived from animal matter) at present have the largest 
number of adherents, and in respect, at any rate, of certain descriptions of petroleum are 

• " Petroleum and its Prodncts." Redwood Boverton. London, Ist ed., 1896 ; 2nd ed., 1906, vol. i, 
p. 254. 

t Contrary opinion held by Eugene Coste. Se<! .Jrmnial of Franklin In.st., 1904, vol. clvii, p. 446. 

3* — Whatatutu. 



30 

the most worthy of acceptance. At the same time, careful study of the subject leads to the 
conclusion that some petroleum is of vegetable origin, and it therefore follows that, as with 
many other objects of controversy, no single theory is of universal application."* 

As opposed to the above, Mr. Eugene Co.ste advances the theory that the origin of natural 
hydrocarbons or petroleum is from the interaction of solfataric volcanic gases. t 

Petroleum-indications. 

The petroleum-indications occurring within the subdivision may be best described under 
the headings : — 
(1.) Oil. 
(2.) Gas. 

(1.) Oil. — Occurrences within the Subdivision. — Good surface indications of oil occur at 
Waitangi Hill, at a point 69 chains slightly south of west from Trigonometrical Station 138, 
on a head-water branch of the Te Hau-o-te-atua Stream. This small branch has been named 
Petroleum Stream on account of these indications ; for in a length of 16 chains of its course 
seepages of oil may be seen at fourteen different points. 

The main oil-spring stands at an elevation above sea-level of 1,413 ft., on the south- 
west corner of a very slightly undulating area about 100 acres in extent. It is a pool at present 
7 ft. in diameter and 5 ft. deep, with its water-level but little below the level of the surround- 
ing coimtry. On the surface of the water floats a light-brown-coloured emulsion of mud, 
water, and oil (see analysis, p. 38) covered by a film of dark-brown oil, through which gas 
bubbles up freely at the western and eastern ends of the pool. This oil has permeated the 
sandy clay surrounding the pool for distances varying from 1 ft. to 5 ft. beyond its cir- 
cumference. 

At 10 ft. west of the edge of the main oil-spring is a pool of water 35 ft. by 12 ft., which 
shows inflammable gas bubbling up sparingly, but no oil. 

At 250 links south-west of the main spring is a test-pit {9a)J 3 ft. by 5 ft. 6 in., which 
now has a depth of 19 ft., but is reported to have reached a depth of 100 ft. Water has risen 
in the pit to within 18 in. of the surface-level, and shows a covering of mud, water, and oil 
emulsion and a film of dark-brown oil, as at the main oil-spring. Gas bubbles up constantly. 

About 200 links south-west of the main spring are two seepages (Nos. 9b and 9c) within 
a few feet of one another. There are slight depressions on the surface of the ground, about 
9 ft. by 5 ft. in area, containing numerous minor holes full of water, the surface of which is 
covered by a thin film of oil. The sandy clay within the depressions is saturated with oil, 
while portions, consisting of a mixture of petroleum with a vers- small amount of clayey 
material, have solidified (see analysis 2, p. 38). 

At 430 links slightly west of south from the main oil-spring is a small sink-hole (8a), very 
slightly depressed below the surface, showing material saturated with petroleum, but no 
pools. 

About 4 chains south of the sink-hole, 8a, are two seepages. One (7a), 6 ft. by 3 ft. 6 in., 
is an area of blackish mud "nith shallow water-holes, covered ■nith a thin film of dark-brown 
oil ; the other (7b) has an area of 12 ft. by 9 ft. 6 in. thoroughly saturated with oil, and has 
a similar appearance to 7a. 

Fourteen feet to the west of 7a a test-pit (7c) 6 ft. by 4 ft. 6 in. has been sunk. At pre- 
sent this pit has a depth of 9 ft., and is fiUed with water to within 1 ft. of the surface. Floating 
on the surface is an emulsion of mud, water, and oil, covered by a film of thick brown oil. 
Gas bubbles up freely through the surface coating. 

* " Petroleum and its Products."' vol. i. p. 261. 

t " Petroleums and Coals compared in their Nature, ilode of OccuiTeuce. and Origin,'' .Journal of Canadian 
Mining Inst., vol. xii, 1909. See also Coste, E., " Volcanio Origin of Oil." Journal Franklin Inst., 190-i, 
vol. olvii. pp. 443-54. 

J For relative position of oil-springs, test-pits, &c., see map opposite this pa^e 



7b acrrmpccny BxilUXirv 2f^ 9 . 




tf Anthtrrtt Jthm Katkmt. e*MmmmKt Printtr 



yoo.e 'O./e* 



To faux p. 3€ 



Jb aciontpcmy Bulletin' iV? 9 . 




*|r 4a(/iorrt« AAn Mnoliay. Otntntmuit Primtmr 



TOa.e lO.ie-i- 



To face p. 36. 



37 



Six feet to the south of 7c is another test-pit (7d) 5 ft. by 4 ft., and 7 ft. in d('j)tli. Tliis 
shows practically no oil or gas-bubbles. 

At a point about 5 chains down the stream occur three sink-holes (Oa, Ob, and 6c) with 
surface-areas, up to 4 ft. in diameter, of clay saturated with petroleum. About 20 ft. distant 
from these occurs a small seepage (6d) showing a little free oil. 

At a distance of 3 chains south-west of the group 6a-6d is the seepage 5a. It is a water- 
hole, partly artificial. 10 ft. by ft., and 2 ft. 6 in. deep, covered by a livownish crust of mud, 
water, and oil emulsion, above which is a little light-brown oil. Tiio ground immediatels' 
surrounding it is saturated with oil. A narrow strip of ground, for 40 ft. in a south-west 
direction from this point, is also saturated with oil, due either lo oil-seepages or to its 
being the channel for the " run off '" of the water. 

At a distance of 35 chains south of the main oil-spring is a very small oil-seepage. Here 
an area 2 ft. in diameter is saturated with oil, and a little free oil is showing. Two chains 
to the west of this a borehole has been sunk. This borehole was commenced with a diameter 
of 8 in.. afterward.s reduced to 6 in., but no particulars are available as to its depth, or the 
rock penetrated. The casing is now filled with water, which shows a verv thin scum of oil 
on the surface. 

The oil of the surface-shows on Waitangi Hill lias probably risen up a tissure or fault - 
plane which has penetrated an oil zone situated at some depth below the surface. 

Occurrenceii without the Lthuts of the Subilivision. — Outside the subdivision, but at no 
ver)' great distance from it, surface indications of oil have been found. Towards the head 
of Totangi Stream, a right-hand branch of the Wharekopae River (Waikohu Survey District), 
and distant five miles south of the southern boundary of the subdivision, is an oil-seepage 
on the line of a probable anticline. Some distance inland from Tuparoa, on the east coast 
of the Raukumara Division, oil-springs also occur. 

Analyses of the Oil. — Some samples of the petroleum occuiring at Waitangi Hill have 
been submitted for analysis in order to determine the nature of the products of which it is 
composed. The analyses are appended, and with them, for comparison, are the analyses of 
oil obtained elsewhere in New Zealand : — 

No. 1. From test-pit 9a, 250 links south of main Waitangi spring. 

No. 2. From main Waitangi spring. 

No. 3. 

No. 4. .. ,. after dry season. Low percentage of kerosene-oil 

probably due to recent burning off. 
No. 5. From New Plymouth borehole, near Breakwater, 1908. 
No. 6. From New Plymouth, 1906. 
No. 7. From Greymouth (results calculated after eliminating 26-5 per cent, of water in 

sample), 1903. 
No. 8. From Kotuku, near Greymouth, 1906. 





(1.) 


(2.) 


(3.) 


(4.) 


(5.) 


(«.) 


(7.) 


(8.) 


Water 


0-3 


0-2 


Nil 


Nil 


2^7 


Nil 


Nil 


Nil. 


Petroleum spirit (benzene) distil- 


0-2 


0-.5 


Nil 


Nil 


140 


20^2 


21 


41 


ling below 150°C. 










(S.G. 
•7426) 


(S.G. 
•7601) 


(S.G. 
•755) 


(S.G. 
•7594) 


Kerosene or buming-oil distilling 


41(> 


390 


47-2 


25-2 


390 


42^8 


28-7 


42-4 


between 158°(". and 300°C;. 


(S.O. 


(S.G. 


(S.G. 


(S.G. 


(S.G. 


(S.G. 


(S.G. 


(S.G. 




•8450) 


•8344) 


•836) 


•842) 


•8317) 


•8351) 


•8026) 


•8443) 


Lubricating-oil distilling above i 


.58-5 


603 


( 51-7 


71-8 


20^5 


22-1 1 




( 47-8 
(S.O. 


300°C. 


(S.G. 


(S.G. 






'. 


.56-2 


Paraffin ) 


•9107) 


•9002) 


( M 


30 


14-5 


10-3 ) 




( -9024) 


Pitch 








. . 


93 


4^6 


12-85 


5^2 


Loss 
















0-5 




inon 


1000 


1 00^0 


lOO^O 


1000 


1000 


99^85 


100-0 



38 

From the results of the analyses of the samples of oil from Waitangi Hill (excluding 
No. 4, which was taken under unfavourable circumstances — ^thc weather had been very dry 
for some two months previously, and the oil had been recently burned off), it will be seen 
that the kerosene or burning-oil averages about 40 per cent. The oil is therefore valuable as a 
fuel, and can be used in its crude state for various purposes, amongst which not the least is 
the generation of steam-power. 

It resembles the oil from Kotuku, Westland, more than the oils of Taranaki. The latter, 
it will be seen from the analyses, have a much higher percentage of the lighter variety of oils 
— benzene and kerosene. It must, however, be borne in mind when making such comparisons 
that the samples from Waitangi have been taken from oil appearing at the surface, while those 
from Taranaki have been taken at some depth below the surface. 

From the reports made by the late Mr. W. Skey, formerly Public Analyst, it would appear 
that he considered that, should oil be obtained from a borehole of some depth at Waitangi 
Hill, it would have a lower specific gravity than that now appearing on the surface. Thus 
it would have a higher percentage of the lighter oils, and consequently a greater value as a 
heating agent, than the surface oil.* 

For the sake of comparison the table appended gives the results of the analyses of samples 
of oil obtained in various parts of the world which show a similarity in composition to those 
obtained from Waitangi Hill.t 



Mexico 

,, . . . . 

Roumania . . 

,, . . . . 

Newfoundland 

Persia 

Java 

Samples of the petrolised clay surrounding and in the vicinity of the springs at Waitangi 
Hill ; the mud, water, and oil emulsion referred to as occurring on the main oil-spring, test- 
pit 9a, test-pit 7c, and the spring 5a ; the portions of highly petroliferous matter referred 
to as separating out from seepage 9b, have been submitted for analysis, with the following 
results : — 



Speciiio 
Gravity. 


Kerosene. 


Intermediate 
and Lubricating 
Oils with Solid 
Hydrocarbons. 


Coke 


•874 


37-0 


62-25 


0^5 


•882 


27^75 


66-0 


, , 


•839 


57^25 


41-2 


1-3 


•890 


27-5 


64-15 


2-6 


•843 


37^6 


58^6 


2^1 


•846 


47-3 


47-8 


2-7 


•881 


46-8 


46^1 


7-1 





(1.) 


(2.) 


(3.) 


(4.) 


(5.) 


(6.) 


(7.) 


(8.) 


Moisture 


3-65 


5-81 


2-12 


39-20 


7-90 


8-25 


2-06 


4-81 


Petroleum 


20^08 


26-02 


3-1.5 


17-72 


Nil 


7-10 


13-72 


20-40 


Volatile matter other 


















than petroleum . . 


U-47 


40^41 


11-20 


38^98 


11-94 


29-54 


5-62 


18-69 


Ash 


62^80 


27^76 


83-53 


4-10 


80- K) 


.55-11 


78-60 


56-10 



10000 



100-00 



100-00 



100-00 



100-00 



10000 



100-00 



100-00 



(1.) Highly petrolised clay, which has to some extent separated from the petrolised clay, main oil-spring. 

(2.) Ditto, ditto, from seepage 9b. 

(3.) Vegetable material, 20 ft. south of main oil-spring. 

(4.) Mud-and-oil emulsion from test-pit 9a. 

(5.) Surface material in vicinity of seepages and test-pits 7a, 7b, 7c, and 7d. 

(6.) Petrolised sand and clay, main oil-spring. 

(7.) Petrolised clay, test-pit 9a. 

(8.) Petrolised clay, south edge main oil-spring. 



* Note by J. M. Bell. — Subsequent to the writing of this report a flow of oil of two or three baiTels per 
diem was struck at 655 ft. in the Gisborne Petroleum Company's bore at Waitangi Hill, located by Mr. Adams 
and myself. The analysis of the oil is as follows :— Per Specific 

Cent. Gravity. 

Oil distilling below 150°C. (naphtha, Ac.) . . . . . . . . . . 34 -7422 

Oil distilling between 150°C. and 300°C. (burning-oil) . . . . . . 40-5 -8235 

Residue left in still (heavy lubricating-oils, paraffin, &c.) . . . . . . 25"5 

These results fully bear out Mr. Skey's surmise. lOO'O 

t Taken from " Petroleum and its Products," by Boverton Redwood, 2iid edition, vol. i, pp. 214-16. 



I'LAI'E III. 




M.\:n i*i:i i{()i,i:i m Si'kim;, Waiiwi.! IIii.i, 





Flood I'i,.\:x ok \Va!N<;.\1!()Mi.\ Stkkam. 



liiillitin \'o. ,9.] 



[Fore p, .ts. 



39 

From these results it will be seen that the clay is to a large extent saturated with oil. 
The quantity of material available is not, however, sufficient for it to be of commercial valne 
for the production of petroleum by distillation. 

(2.) Gas. — General Occurrence.— The strata yielding gas are geologically identical with 
those yielding oil. Gas is the invariable accompaniment of oil where conditions favour its 
accumulation — that is, where the reservoir or porous stratum is overlain by an impervious 
one which will prevent the escape of the gas to the surface. 

Gas, oil, and water occurring in a zone where compression has produced folding of the? 
strata without faulting will under favourable circumstances occur in three layers. The gas 
will form the highest layer, and will rise to the arch of the anticlinal folds, the oil will form 
the middle, and the water the lowest layer. Where strata with which an oil zone is associated 
have a monoclinal or anticlinal arrangement with the development of undulatory struc- 
tures at two or more levels it is possible that wells sunk on the highest of these undulations 
will produce gas alone, while wells sunk on the next lowest terrace will produce oil. 

Wells producing gas are of economic importance when the supply of gas is sufliciently 
large to be useful for heating and lighting purposes. The life of these wells is, however, not 
a very long one, and at all times pressure (and therefore the flow of the gas) is influenced 
by variations in the atmospheric pressure, and, in the vicinity of the sea. by the rise and fall 
of the tide. 

The primary pressure of gas in a well varies according to tlie aiiiingeinent of the strata 
and to the depth of the well : pressures as high as 1,()0(J lb. per si|uarc inch have been recorded. 
The pressure is due to the gradually accumulating gas having had no opportunity of escape, 
and to it — assisted, perhaps, in some cases by water in the strata under hydrostatic 
pressure — may be attributed the spouting of oil-wells. 

Occurrences of Gas-emanations u'ithin and near the Subdivision. — A small number of gas- 
occurrences have been noted within and close to the boundaries of the subdivision. Gas 
accompanies the oil which appears as a film on the surface of the water at the main oil-spring 
and on test-pits 9a and 7c at Waitangi Hill. It occurs unaccompanied by oil in \\w water- 
pool 15 ft. to the west of the main oil-spring. 

In the present Waitangi l)oreliole gas was struck at a depth of ;5I1 ft. In the South 
Pacific borehole the reported large quantity of gas struck was said to be responsible for the 
burning-down of the derrick, wliiie in the Minerva borehole a considerable (juantity of gas 
is said to have been struck. 

Numerous g^as-vents, which are now no longer active, exist within the subdivision. The 
positions of three of these have been marked on the map accompanying this report — namely : — 

(1.) On the right bank of the Waipaoa River about 25 chains above the mouth 

of the Mangaorango Stream. 
(2.) On the left bank of the Waihora River 5() chains below its confluence with 

the Motumate Stream. 
(.3.) On the left bank of the Waihora River 45 chains west of Paraeroa homestead. 

No. 1 may be derived from an oil zone. It appears to be on a fault-line in this vicinity. 
Nos. 2 and 3 appear to be on a break produced by a slump or large landslide from the spur 
on the south side of the Waihora Stream, and possibly derived their gas from the decay of 
vegetable matter but a short distance below the surface. 

In the bed of the Mangaorango Stream and on the spur to the north of Weraroa Stream 
occur gas-vents, situated in each case about half a mile above the northern boundary of the 
subdivision. 

At Waimata, four miles outside the southern boundary of the subdivision, the pressure 
of the gas-emanations is at times sufficient to produce a considerable extravasation of mud 
and stones.* 



* See New Zealand Mines Record, October, 1908. 



4U 

A. Siiiuple of the gas eiiiitted at the laaiii oil-spring on Waitangi Hill was sulnuitted ioi 
analysis with the following result : — Pei- Cent. 

Methane, or marsh -gas (CH^) ... . . . . 96-5 

Carbonic anhydride (CO^,) . . . . . . . . . . 3-5 

lOU-O 
Probable Oil Zone. 

Of the ten or more boreholes which have been sunk within the subdivision, in not one 
instance are samples of the rock bored through available. The rocks passed through are 
generally described briefly and unscientifically in the logs of the various boreholes. For 
this reason the logs are of value only to indicate some very marked change of rock, the depth 
at which a flow of underground water occurs, and the depth at which gas and oil indications 
were found. If in conjunction with the logs samples representative of the rocks passed through 
in driUing had been carefully preserved, reliable records would now be available. 

Of the wells sunk within the subdivision, in only one instance is even a log available. For 
infonnation, therefore, regarding the probable oil zone of this area the geologist is entireh' 
dependent on the rocks which have been exposed by degradation in stream-beds, cliffs, 
landslips, &c. 

As a result of the examination that has just been completed it seems certain that the clay- 
shales which fonn the lowest beds of the Whatatutu Series are the upper portion of, or form 
an impervious cover for, the oil zone of this area. Every sample of this rock which was obtained 
gives when finely pulverised and subjected to strong heat a decided smell of hydrocarbons. 
From its characters the clay-shale is admirably suited for a cover for a stratum containing oil. 

This rock is exposed at the surface in the head-water valleys of the Mangatahu and Wai- 
tangirua streams, and will occur at some, perhaps considerable, depth at Waitangi Hill. From 
this one exposure at the head-waters of the Mangatahu and Waitangirua streams it is not 
possible to estimate the depth at which it occurs at the boring-sites which have been recom- 
mended, since the overlying beds of chalky limestone and glauconitic sandstone, &c., probably 
vary to some extent in thickness. Also, one or more of these overlying beds may be absent 
at the particular site chosen. 

Sites for Boreholes. 

From a report on " The Oilfields of Texas-Louisiana Coastal Plain.""* the following extract 
has been taken : — 

" In many regions it is comparatively easy for the geologist, by an examination of surface 
indications, to state definitely and with certainty that no oil in commercial quantities will be 
foimd. In other large regions he can state that oil may be found, and can point out in some 
cases the most favourable localities, but he cannot predict the actual occurrence of an oil-pool 
in advance of drilling." 

In the case of the Whatatutu Subdivision it can be definitely stated that oil may be found, 
and, moreover, the most favourable sites for drilling may be pointed out, but it must be borne 
in mind that the WTiter does not say that boring will with certainty be successful. 

In the recommendation of sites for boreholes which is made in this report it has been 
assumed that a domal arrangement of beds is the most favourable for the maximum accu- 
mulation of oil. At the three sites recommended the general arrangement of the surface beds 
has in each case been described on pages 26, 27, 29. Here, therefore, only a few remarks con- 
cerning the sites will be necessary. 

(1.) The Dome of the Toromiro Anticline. — In this locality the site for a borehole as marked 
on the map is a short distance to the south-west of the supposed actual apex of the dome. 
This apex has an elevation of 1,120 ft., t while that of the site proposed is about 800 ft. t 
The apex of the dome is covered by beds of argillaceous sandstone and claystone, while at 



* U.S.A.G.S. Bulletin No. 212, 1903, p. 140, by Hayes, C. W., and Kennedy, W. 
■|" Barometric heights. 



41 

the boring-site a certain amount of degradation of this material has taken place. The site 
recommended should be no less favourable than that of the apex, since, as has been 
before stated, the actual domes may be gas-producing only. Moreover, since a portion of 
the argillaceous sandstone and claystone beds has been removed from the underlying lime- 
stones, and as the angle of dip of the argillaceous sandstones and claystones does not increase 
very rapidly, a less thickness of strata should have to be drilled through at the proposed site 
to reach the supposed oil zone than at the apex of the dome, which has :5(K> ft. greater elevation. 
The site as proposed is more accessible for transport of machineiy, &c., than the apex of the 
dome. On the map of the Waingaromia Survey District will be found represented the bridle- 
track leading from the Gisbome-Waiapu Inland Road towards this point. The point at 
which this track leaves the road has an elevation of about 1.200 ft., while the point at which 
it reaches the streara-bed has an elevation of about 700 ft., so that in a distance of three- 
quarters of a mile there is a fall of some 500 ft. By taking a less direct line down the spur 
there would, however, be no difficulty in making a road with a grade less than 1 in 8 to this spot. 

(2.) The Dome of the \Vaita)tyi Atiticlixe at Waitangi Hill. — This site has already been 
proposed as a suitable one for boring,* and on it the Gisborne Oil Company is at the present 
time engaged in sinking a well. 

The site has an elevation of 1,450 ft. above sea-level, and is distant about live miles from 
the village of Whatatutu. The road by which the machinery, &c., were transported is un- 
formed. For about two-thirds of the distance it follows the bed of the Mangataikapua Stream, 
then rises up a spur on the east side of the valley between the main stream and a large left 
branch. The grade of the latter part is very steep, but can be negotiated with a fairly heavy load. 

The reasons for recommending this site have already been stated in a former report,* 
but are here given in extenso. 

(1.) It lies at or near the crest of a longitudinal anticlinal fold, and near the point of 
transverse folding on that longitudinal fold — in other words, at or near the point 
of doming in the strata. 
(2.) It is apparently removed from " slip " country, so prevalent in this country. 
(.S.) It appears to be removed from the possible line of fault along the petroleum- 
springs. 

As far as can be estimated from the outcrops in the vicinity, glauconitic sandstone should 
be met with at about 500 ft., and chalky limestone at from 800 ft. to 1,000 ft. As will be 
seen by reference to pages 12 and 40, the probable oil zone lies below this chalky lime- 
stone, and therefore this bed, and possibly the day-shale underlying it, must be penetrated 
before oil in payable quantity can be expected. 

Indications of oil and possibly a small amount of oil may be obtained within the glauconitic 
sandstone and chalky limestone beds ; but the absence of such should not be taken as a proof 
that no oil will be obtained, until the supposed oil zone has been reached. Their absence 
should rather be taken as proof that the underlying beds are sufficiently impervious and so 
little fractured as not to allow of the escape of the oil from its proper zone.f 

• See Second Annual Report of the N.Z. Geol. Surv., 1908, pp. II, 'i-y. 

t Note bv .1. M. Bell. — The deductions made by Mr. Adams have been borne out to a remarkable degree 
by the records of the Waitangi borehole. As judged by samples submitted to me, the following strata have 
been encountered as measured from the surface to the greatest depth attained by the 1st December, 1909 : — 

360 ft. Grey glauconitic claystone. 

370 ft. Light-grey claystone. 

380 ft. Glauconitic sandstone. 

390 ft. Fo.s.siliferous green sandstone. 

410 ft. Dark-coloured claystone. 

478 ft. Hard indurated claystone. 

522 ft. Friable green sandstone. (This stratum was reported to contain gas.) 

H.50 ft. Dark-grey claystone with streaks of glauconitic sandstone, and exhibiting a distinct odour of 
petroleum. 

655 ft. Highly friable pepper-grey claystone, containing oil. 

825 ft. C.il<areous clivystone. 

901 ft. Calcareous claystone or argillaceous chalky limestone. 



42 

(3.) Tlic Domr of the. Waitangi Anliclinr on the. Western Side of the Mangatu River. — The 
site proposed for boring in this kjcality is a short distance to the south-west of the supposed apex 
of the dome. The rock forniiiifr the crest of the dome and occurring immediately surrounding 
the proposed boring-site is chalky limestone. At the site it is apparently directly overlain 
by gravels and boulders, which form a low-level terrace with an elevation of about 6 ft. above 
the ordinary water-level of the river. 

The argillaceous sandstones, which appear on the southern slopes of the dome, have 
been removed by erosion from the eastern slope, and probably with them some thickness 
of chalky limestone. 

In the case of this boring-site, therefore, after passing through the terrace gravels, chalky 
limestone should be the first rock to be drilled through. Of the three sites proposed, this is the 
most accessible. It is situated at a distance of about five miles from the village of Whatatutu. 
The Mangamaia Road passes within about half a mile of it, and the remaining half-mile is 
over a flat terrace, up a few chains of the Mangatu River bed, and again on to a terrace. No 
difficulty should be experienced in the transport of machinery, &c., required for drilling purposes. 
As has already been stated, the clay-shale, representing the lowest portion of the Whata- 
tutu Series, is exposed in the head-water valleys of the Mangatahu and Waitangirua streams. 
These exposures occur at an elevation as high as 2,000 ft., on each side of the crest of the 
Raukumara Range. Clay-shale is not exposed in any other portion of the subdivision, 
although the chalky limestones which overlie are exposed over a large area, and in the 
eastern as well as the western portions of the subdivision. 

From this fact one must conclude that geologically, as well as topographically, the north- 
western portion of the subdivision is at a higher elevation than the remaining portion of the 
area. 

A detailed geological survey of those portions of the Arowhana, Ngateretere, and Motu 
survey districts, which immediately adjoin the north-western portion of the Mangatu Survey 
District, will be necessary to prove whether this greater elevation of the beds is not due to 
the occurrence of a dome, or, at least, an anticlinal fold, coincident with or in the vicinity 
of the crest of the Raukumara Range. Unfortvmately, the exposures of clay-shale examined 
in the Mangatahu and Waitangirua streams during the geological survey just completed 
did not show stratification. If the existence of a dome in this vicinity is proved, then this is, 
without doubt, the most favourable position in the whole area for the accumulation of oil and 
for drilling a well to penetrate the probable oil zone. In any case, since it is almost certain 
that these clay-shales are a portion of, or an impervious cover for, an oil zone, a well drilled 
here, though it proved non-productive, would supply very valuable information as regards 
the prospects of obtaining oil. Since the clay-shales are here exposed at the surface, the 
well would commence in beds which can only be reached at some, perhaps considerable, depth 
on the other boring-sites that have been recommended. Therefore the chances of penetrating 
them and reaching the probable oil zone are the better. 

The fact that oil-springs and gas- vents have not up to now been discovered in this locality 
does not at all detract from the possibility of obtaining oil here, but if an oil zone exists at 
some depth it is a proof that the clay-shale covering it has not been fractured sufficiently to 
allow of its escape. 

It is impossible from the amount of information available to suggest any particular spot 
in this locality at which drilling should be undertaken, and still more impossible to predict 
that oil mil be obtained here. Nevertheless, the general geological structure of the area which 
has been examined suggests that it may be a most favourable locality for oil-accumulation. 

Material for Macadamising Purposes. 
The rock formations in the area have for the most part a loosely conapacted texture and 
suffer rapid surface decomposition. For this reason the hill slopes and crests on which the 
highways have been formed are in general covered by a moderately thick mantle of loosely 



43 

consolidated debris and clayey material. The roads have not been macadamised, and are 
suitable only for light traffic in dry seasons. Such outcrops of harder rock as are within easy 
access of these roads are for the most part of so indifferent a quality for roadmaking pui-poses 
that the benefit to be derived from their use as macadamising material would not warrant 
the necessary expenditure. 

Conglomerate. — The most suitable material for macadamising purposes which occurs within 
the subdivision is to be obtained from the bands of conglomerate which form a poi'tion of the 
Upper Whatatutu Series. The locality of occurrence of these bands has already been referred 
to (see p. 18), and further reference need only be made to two of these localities — (1) Con- 
glomerate Stream and (2) Waikohu River. 

(1.) The exposure in Conglomerate Stream is the most suitable for a large supply of mac- 
adamising material. Between the bridge by which the Mangatu \\'aipaoa Stock-track crosses 
this stream and the waterfall over which the stream flows before joining the Waipaoa River 
occur layers of conglomerate striking north-west and south-east, and dipping to the south-west 
at about .30° to 45". The lower bands are very finely textured, tlie largest material not ex- 
ceeding I in. in diameter. The upper bands are considerably coarser, the pebbles averaging 
some 2 in. in diameter, with occasional stones up to 2 ft. The coarsest part of the exposure 
is about 1(J() ft. below the level of the stock-trac k, and distant from it about 16 chains. 

The beds of conglomerate have a total thickness of about 120 ft., with the highest portion 
of the exposure about .30 ft. below and some 10 chains distant from the bridge mentioned above. 

In the event of the Mangatu-Waipaoa Stock-track being widened to admit of wheeled 
traffic, this material would be of great value for macadamising it. 

(2.) This exposure extends over a distance of 60 chains, but consists mainly of finely 
textured material, with its largest pebbles about ^ in. in diameter. One or two bands, how- 
ever, of coarser material were observed in the river-bed, containing pebbles up to 6 in. in 
diameter. The beds strike S. 65° W., N. 65° E. and dip to E. 65° S. at 45°. Seeing that 
the coarser portion of the exposure is within 35 chains of the Te Karaka - Motu Road, 
the approach to which is along a practically level terrace, further investigation to locate, if 
possible, other and larger bands of coarse material suitable for roadmaking is recommended. 

The character of the rocks forming the conglomerate has been described on p. 19, and 
it need only be added that they are sufficiently hard to resist crushing under heavy traffic. 
With a foinidation of 5 in. spawls, covered by material broken to pass a 2 in. ring, and bound 
and blinded by a covering of the finer-textured conglomerate, a road capable of standing 
heavy traffic should be obtained. 

Burnt Papa. — Burnt " papa " or claystone has been used for roadmaking purposes in the 
Whangamomona Settlement, situated twenty-eight miles north-east of Stratford, for over ten 
years. The burnt papa is most economically produced by buniing the papa in kilns holding up 
to 400 cubic yards, built up against a selected papa batter at the roadside. To build the kiln the 
papa is picked and blasted on to a layer of firewood until the latter is well covered. This in turn 
is covered by a layer of firewood, and the process repeated until the desired quantity of papa, 
separated by layers of firewood, is included within the kiln : the whole is then blinded and 
the wood fired. The burning-out of the wood layers will occupy several days, but during 
that time the kiln requires no attention. 

The economic production of " l)urnt papa " depends on the available supply of firewood 
and the natural suitability of the site for a kiln. The factors for consideration in the latter 
case are the amount of earth-stripping required to expose a good face of papa, the ease with 
which the burnt material can be handled from it, and its relative position to the whole of the 
road as a depot from which the material is to be hauled. The papa (claystone) to be burnt 
should be argillaceous rather than arenaceous in character. 

For light traffic, where it is laid on lengths of road accessible to the sun, burnt papa stands 
excellently ; the maintenance of shady parts of the road made with it is expensive. It may be 
considered an economic substitute for macadamising material when laid on roads exposed 



44 



to the sun and subject to liglit traffic, if the cost of burning and laving tlie material does not 
exceed lUs. per cubic yard.* 

Materials for Cement-making, etc. 

Limestone. — Exposures of limestone cover a moderate area of tlie subdivision, and in 
order to determine their value for the manufacture of cement, samples from various localities 
liave been submitted for analysis. The results of these analyses are appended : — 

(1.) From Makahakaha-Xgarara Stream, above confluence with Melissa Stream. 

(2.) From Subtrigonometrical Station A, Mangatu Survey District. 

(3.) From Slip Stream (small right-hand branch of Waipaoa River). 

(4.) From Waipaoa River. l)et\veen first and second road-crossings, above Mangataikapua 



homestead. 


(1.) 


(2.) 


(:«.) 


(4.) 


Silica (SiOa) • . 


. 5-40 


3-05 


20-52 


11-55 


Alumina (AUOg) 


. 0-48 


7-44 


6-28 


2-81 


Ferric oxide (FeOj) 


. 0-96 


114 


1-92 


1-28 


Lime (CaO) . . 


. "50-78 


47-24 


37-25 


45-56 


Magnesia (MgO) 


. 0-60 


0-25 


0-10 


0-50 


Carbonic anhydride (COo) 


. 39-90 


37-12 


29-.30 


35-80 


Moisture 
Organic matter 


. 0-40) 
. Nil j" 


.3-73 


3-30 


1-60 


Alkalis (K2O, NajO) . . 
Undetermined 


' 1-48 

1 


0-03 


1.33 


0-90 



100-00 100-00 100-00 100-00 
As will be seen from these analyses, No. 1 contains the greatest percentage of carbonate of 
lime (CaO-f-COj = 90-68 per cent.), and. although containing a small percentage of free silica, 
is a fairly pure limestone. In general these analyses show a content sufficiently low in ferric 
oxide, magnesia, and free silica, and sufficiently high in carbonate of lime, to be useful for 
cement-making. With the exception of No. 2 the samples are from exposures of limestone 
which have a tendency to flake on exposure, and should be readily pulverised. 

The chief economic factor in cement-manufacture is suitable geographical position — 
that is, a position from which the manufactured article can be cheaply and readily distributed 
and exported. This advantage the subdivision unfortunately does not possess. A second 
important factor is a cheap and abundant supply of fuel, preferably coal. Up to the present 
time a workable coal-seam has not been located within an easy distance of the limestone, 
deposits. These two drawbacks alone would preclude competition with more favourably 
situated localities, and cement, if manufactured within the subdivision, must therefore be 
confined to the supplying of local requirements. 

Claijs. 
Samples of clays taken from the surface bores at Waitangi Hill were submitted for analysis 
in order to determine their composition. The results of the analyses are appended : — 

Silica (SiOj) 

Alumina (AI2O3) 

Iron-oxides (Fe,0.,) 

Lime (CaO) 

Magnesia (MgO) . . 

Loss at red heat 

Alkahs and undetermined . . 



* The ^\Tite^ is indebted to Mr. E. C. Robinson, civil engineer, Stratford, for the information concerning 
burnt papa. 



(1.) 

. . 65-9 


(2.) 
60-5 


. . 18-1 


17-5 


2-6 


2-0 


0-9 


4-5 


0-7 


0-6 


9-4 


12-2 


2-4 


2-7 


1000 


1000 



45 

Sample (1) was taken from a 5 ft. band of very plastic clay occurring 5 ft. below the surface 
in No. 1 surface bore. Almost the whole of the material taken from this borehole to a depth 
of 29 ft. consists of plastic clays with occasional small sandy layers. Sample (2) was obtained 
from a 5 ft. band 40 ft. below the surface in No. 2 bore. The material from this bore to a 
depth of 45 ft. consists mainly of plastic clays with a few layers of sand and sandy cla}-.* 

Similar clays to those from which the above samples were taken occur in many parts 
of the subdivision. From the analyses it will be seen that the percentage of iron-oxides is 
too high for the clavs to be of value for fine pottery or firebricks, but since they are very 
plastic they should make good bricks. 

Reference has been made to the use of burnt claystone for macadamising purposes 
(see p. 43). 

In many parts of the subdivision the rocks decompose, and liecome reduced to a mix- 
ture of clay and very fine sand. This material, in the wet seasons, is carried down by the 
water escaping to the streams, and on meeting a slight obstruction, or on reaching a flat 
space where the transporting-power of the water is diminished, is deposited in the form of a 
wet pasty mass ; such masses often attain a depth of 2 ft. or more, and cover several square 
yards. These are what might be termed " running slips," as fresh material is continually 
being carried down. They are a cause of much trouble to the sheep-farmers, owing to the 
fact that the sheep, in attempting to cross them, become stuck fast or bogged. It has been 
found that in a number of cases the animals seek out these running slips in order to eat the 
clayey material. 

Two samples were sent for analysis from slips which in this wa\- have proved death- 
traps to so many sheep. The results of the analyses are appended : — 

Silica (SiO..) 
Alumina (Al^Oj) 
Iron-oxide (Fe^Oj) 
Lime (CaO) 
Magnesia (MgO) 
Alkalis (Na,0, K.,0) 
Organic matter and moistun 
Undetermined 



Soluble in water at 15-5°C. 

The soluble matter in these clays consists mainly of common salt, but the analyses show 
that otherwise there is nothing unusual in their composition. It is almost certain that it 
is for the salt content that the sheep eat the clay, and it has been found that when boxes con- 
taining salt are placed on the tracks leading to these slips the number of bogged sheep is largely 
diminished. 

Goi-D. 

A small amount of prospecting for gold has been carried on within the subdivision, 
especially while the greater portion of the area was still covered with bush. Small pieces of 
quartz containing gold are reported to have been found, but attempts made to locate an auri- 
ferous vein have proved unsuccessful. The general rock formation of the area certainly suggests 
that these erratics of auriferous quartz have been derived from veins situated in some other 
district, and it is indeed highly improbable that quartz veins carrying gold will ever be located 
within the area covered by the subdivision. 

Small pieces of quartz are included in the conglomerate bands which have already been 
described (see p. 18), but such as were seen bv the ^vTite^ of this report are of a decidedly 



(1.) 


(-2.) 


. . 61-2 


55-7 


. . 19-0 


11-4 


. . 2-1 


4-5 


. . 1-7 


11-8 


. . 1-6 


1-4 


. . 2-2 


2-3 


. . 100 


10-1 


. . 2-2 


2-8 


100-0 


100-0 


. . 10 


0-9 



* bee page 2. 



46 

" hungry " appearance. Dishes of material taken from these bands were carefully washed, 
but in no case was even a " colour " of gold obtained. The chances, therefore, of obtaining 
alluvial gold from this formation are practically negligible. 



Coal. 
No evidence of the occurrence of payable coal-seams was obtained during the survey of the 
area. If such do occur they are not exposed at the surface, and their presence will probably 
only be detected by deep boring. 

A sample of lignite, said to have been obtained fi-om the Whatatutu Subdivision, has 
been analysed at the Dominion Laboratory. The result of the analysis, with the remarks 
of the Dominion Analyst on the same, is appended : — 

Fixed carbon . . . . . . . . . . . . 8-38 

Volatile hydrocarbons . . . . . . . . . . 35-32 

Water . . . . . . . . . . . . . . 26-13 

Ash .. .. .. .. .. .. .. .30-17 



lOO-OO 



" The sample is a lignite with an excessive amount of ash, and is of very poor quality." 

Mineral Spring, 

On the crest of the ridge separating the Waikohu River and the Urukokomoku Stream 
occurs a mineral spring. The spring is situated at the head of the Waikohuiti Stream (see map 
of Mangatu Survey District), within half a mile of the Te Karaka - Motu Road, and is easily 
accessible. 

In order to determine the natm'e of the salts in solution, a sample of the water was sub- 
mitted for analysis. The result of the analysis is appended : — Grains per 



Sodium-chloride 

Sodiima-silicate 

Sodiimi-sulphate 

Aluminium-svdphate 

Iron-sulphate 

Calcium-sulphate 

Magnesium-sulphate 

Iodides 



Gallon. 

6-5 

9-0 

53-0 

93-0 

1-5 

34-0 

13-5 

Nil 



Total solids . . . . . . . . 210-5 

Free carbonic anhydride (CO,) . . . . . . . . 3-5 

The water is rather remarkable for the large amount of siilphate of alumina present. 
In this respect it resembles a water from White Island Lake, and water from Taheke Spring, 
Rotorua. It differs from these, however, in containing no free acid. The absence of free 
acid may be due to the original acid content having acted on the rock through which it has 
passed to reach the surface, thus forming sulphates of aluminium, sodium, iron, &c. 



INDEX. 



Agriculture 
Ahititi Peak . . 
Analyses 13, 14, 

Anticlinal theory 
Anticlines 
Arakihi Peak . . 
Arakihi, post-olHce at 
Arakihi synclinc 
Area of subdivision 
Argillaceous sandstone 



V. Page 

1-4 

8 

5, 16, 37, 38, 40, 44, 45, 40 

24 

. . 23, 25, 26-30 

8 

5 

. . 25, 26 



15, 16, 25, 2(;. 
31. 33 



B. 
Basalt 
Bell, J. M., log inserted by 

„ notes bj' 

Big or Waipaoa River 
Big Slip 

Big Slip Fault.. 
" Blow-out " of oil and 
Borehole, Minerva, 

„ surface 

,, South Pacific. 

,, Totangi 

„ Waitangi 

log of 
Brachiopoda . . 
Burnt papa for roads 
Bu-sh 
Butter-factories 



27, 29. 30, 



. 19, 20 

6-8 

. 38, 41 

8 

8 

. 30, 33 

5 

6 

2^ 

5 

6 

4, 6, 41 

6-8 

22 

43 

. 2, 4 

1 



13, 14, 15, 17, 
13, 14, 28, 



C. 

Calcite 

Cattle- raising . . 
Cement- materials 
Chalk}- limestone 
Chert- breccia . . 
Clays . . 

„ analyses of 

,, occurrence of salt in 
Clay-shale 
Claystone 13, 15, 16, 25, 26, 27, 28, 29, 

32, 33 
Coal .. 

Coastal plain . . 
Communication, means of 
Concretions . . 15, 16, 23, 25, 

„ nuclei of . . 

Conglomerate 16, 18-20, 23, 28, 29, 31, 33 
Costc, Eugene, volcanic oil theorj' of 
Cox, S. H. 

Cretaceous rocks, supposed 
CitcuUaea 

D. 

Dair^'-farming 

Debris, looselj' consolidated and uncon- 
solidated 

Decomposition of rocks 

Dentalium giganteum 

Depression of land 

Diorite 

Dip of strata {see a'so Anticlines, Synclines, 
Structure) 23, 25, 26, 27, 28, 29, 

Dolerite 

Dolomitic concretions and rocks 

Domes . . 24, 25, 26, 27, 29, 40, 



2, 13, 



19, 30 
1 

44 
29, 30 

16 
44--i5 

45 

45 

12,30 

30, 31, 

46 

9, 10 

4 

26, 27 

16 
43, 45 

36 

10 
12, 23 
21, 22 



1 

9, 32 

32, 45 

14, 22 

10 

19, 20 

30, 31 
19,20 
16, 17 
41, 42 



Echinodermata 
Elevation of land, &c. 



E. 



K. 



22 
9, 10 



Faults 6, 29. 30, 32-34 

Field operations, method of conduit inf; . . 2 

Folding . . . . 10, 23, 24, 25 

Foraminifera . . . . . . 13, 14, 20, 32 



Fossiliferous argillaceous sandstone 



Fossils 



Page 
17, 20, 25, 26, 
27, 28, 29, 30 
14, 17, 21-23 



(I. 



Gabbro 
Galvin, P. 
Gas, occurrences of 
,, analysis of 
,, vents 
Ga.stropoda 
Geological history 

,, investigations, piwious 

„ .sequence 

,, work, conditions of 

Gcologv, outline of 
Olauconite and glauconitic sand.stonc 

Gneiss 

Gold . . 

Gordon. H. A. 

Granite boulders in King-country 

H. 

Hanging valleys 

Hauiti, telephone Ijureau at 

Hector, Sir James 

Hill, H. 

1. 

Ice transportation of conglomerate, suppo.sed 
Igneous rocks, material derived from {see 

also Congloraerate) 9, 18, 19, 20 

Indurated bands 17, 26, 27, 28, 29 

Inoceriimux not found . . . . . . 16, 23 

Inorganic origin of oil theory . . . . 35 

Iron-o.xidc concretions . . . . . . 15 

Iwiroa, po.st-office at . . 5 

K. 

Kahikatea . . . . 4 

Kaniahi, or towai . . . . 4 

Kowhai . . . . 4 

Kaiiaekanae, post-oflice at . . 5 



19 

.. 10, 11 

5, 37, 39-40 

40 

33, 34, 39 

22 

10 

2 

9 

2 

. . 9-10 

14, 15, 21, 

27, 28, 30 

19 

.. 45-46 

10 

19 



2, 10 
10, 11 



19 



Lignite, analysis of . . ■ ■ 46 

Limestone . . 13, 14, 16, 17, 20, 44 

Literature, list of .. .. .. 10-11 

Little Maungahaumia, .Mount . . 8 



M. 



Macadamising material 
McKay, .Alexander 
Makara anticline 
Mammalia 

Mangajjapa anticline 
Mangatahu Stream 
Mangataikapua River 
Mangatu anticline 
Mangatu River 
Maps 



.. 42-44 

2, 11, 12, 23 

29 

22 

30 

. . 12, 13 

8 

28, 29, 30 

8 

2 



Marshall, Dr. P., palaeontological report of 21-23 

Matai 

Materials for cement {see also Limestone, Clay) 

Maungahaumia, Mount 

,, Mount Little 

.. synclinc 

Track . . 
Means of communication 
Mineral spring. . 
Miner\'a borehole 

„ Petroleum Company 
Miocene age of Whatatutu Series 

,. fossils 
-Molasse, Patagoniaii 
Monocline defined . , 



4 

44 

8 

8 

30 

13 

4 

46 

6 

() 

10, 12, 23 

17, 21-23 

23 

23 



48 



N. 



■Neuberger and Noalhat 
Nodoaaria 

0. 

Oil, analyses of 

., occurrences of, &c. . . 

., seepages and springs 

,, zones 

(See also Petroleum.) 
< )mega syncline 
Organic origin of oil theory 
Ostrea ingens . . 



Page 
11 
13 



. . 37, 38 

2, o, 24, 27, 33, 35-40 

5, 36, 37 

37, 39, 40 

26 
35 
17 



Pakarae anticline . . . . 25 

Pakarae River . . . . . . 8 

Palieontology . . . . . . . . 21-23 

Papa . . . . . . . . 15, 43 

Papa, burnt . . . . . . . . 43 

Paraheka Peak . . . . . . 8 

Paraheka anticline . . . . . . 25, 26 

Parariki syncline . . . . . . 26 

Park, Professor James .. .. .. 11 

Patagonian Molasse . . . . . . 23 

Pelecypoda . . . . . . 22 

Petrography, microscopic . . . . 19-20 

Petroleum . . . . . . . . 35-40 

„ found in igneous rocks . . 35 

„ indications of . . 2, 36-40 

,, industry and history of . . 5 

„ occurrences of . . 36-37 

„ Stream . . . . . . 36 

„ theory of inorganic origin of . . 35 

„ thoorj' of organic origin of . . 35-36 

,, theory of volcanic origin of . . 36 

Physical geography . . . . . . 8 

Poiyzoa . . ' . . . . . . 22 

Postal communication . . . . . . 5 

Prospecting for gold . . . . . . 45-46 

Prospecting for oil (see also Boreholes, Test- 
pits, &c.) 5-8, 36, 40-42 
Puha, railway- and post-office at . . 4, 5 
Pukatea . . . . . . . . 4 

Pulpit Rock . . . . . . . . 14, 15 

Pumiceous material . . 9, 31, 32 

Pyrite . . . . . . . . 13, 15 



Quartz 



Rata 

Raukumara Division, 



Q. 



R. 



13, 15, 18, 19, 45 



boundaries of 
,, industries of 

., oil-indications in 

(See al-'O Oil, Petroleum.) 

Raukumara Range . . 8 

Rejuvenation of streams 

Rewarewa 

Redwood, Sir Boverton 

Rimu 

Rivers 

Road-metal 

Roads 

Roads, material for 

Rock crystal (quartz) . . 

Rock-sections . . 

Rosebud Stream 

Rotalia 

Running slips . . 



Salt, common, in clay 
Sandstone 
Seepages of oU. 
Serpentine 
Shafts, prospecting 



s. 



4 
1 
1 
2 

9, 33, 42 

9 

4 

.. 11, 35 

4 

.. 8, 9 

42 

. . 4, 43 

. . 42-44 

lo 

.. 19-20 

8 

20 

45 



45 



14, 15. 10, 17, 20, 21 

5, 36, 37 

20 

. . 5, 36 



Shallow- water fauna 


Page 
23 


Sheep, eating of cla\- by 


45 


Sheep-farming 


1, 4, 45 


Shelly conglomerate 


. 17, 28 


„ limestone 


. 17, 20 


Shore-line, ancient 


. 18, 20 


Silica, secondary 


14 


Siliceous rocks 


14 


Sites for boreholes 


40 


Skey, William 


. 10, 38 


Slips or slumps 


4, 33, 39 


Sollas, Professor W. J. . . 


. 11, 19 


South Pacific borehole . . 


5 


South Pacific Petroleum Company 


5 


Spring, mineral 


46 


Streams 


8, 9 


Structure of Whatalutu Rocks . . 


. 23-32 


„ general 


. 24-25 


„ detailed 


. 25-32 


Syenite-porphvry of Kawhia 


19 


S.ynclines ". .' (i. 23, 25, 26, 27, 28, 29, 30, 31 


T. 




Te Karaka 


5 


Telephone bureaux 


5 


Terraces 


4, 9, 32 


Test-pits 


), 36. 37 


Theory of inorganic origin of oil 


35 


,, organic origin of oil . . 


35 


Timber 


4 


Toromiro anticline . . . . 24, 26, 40 


,, dome of . . 


. 40-41 


Totara 


4 


Totangi Stream, borehole near . . 


6 


Towai, or kamahi 


4 


Tuarua anticline 


26 


Tuparoa, oil-springs near 


37 


Tutamoe Ridge 


9 



u. 



Upper Wiiatatutu beds 



15 



Viridite . . . . . . . . 13, 21 

Volcanic rocks (see al-io Igneous rocks) . . 19, 20 



w. 

Waihora River 

Waikohu River 

Waimata, telephone bureau at 

Waingaroniia River 

,, bore near 
,, sj'ncline . . 

Waipaoa River 

,, „ bore near 

„ Series 

„ syncline 
Wairere syncline 
Waitangi anticline 



9, 



6, 14, 24, 27, 

27, 28, 



domes of 
Fault 

Hill, boring at . . 2, 5 

,, „ oil at . . . . 5, 33, 

Waterfalls of Tawa Stream 
Weraroa Fault 
Whakauranga Stream . . 
Whatatutu, Village of . . 
Whatatutu beds, lower 
,, „ upper.. 

Series .. .. 9, 10, 

„ Subdivision defined 

Wheao anticline . . . . 24, 30, 

,, River . . 
Wheturua, post-office at 

., Hill, fossiliferous limestone on. . 

Wilckena, Dr. Otto 



8 

8 

8 

8 

5 

6, 27 

8 

6 

12, 32 

28 

30 

28,29 

41-42 

6, 32 

,6,41 

36,39 

17 

29,33 

8 

5 

12-15 

15-21 

12-32 

2 

31,41 

8 

5 

17 

23 



C4l '6f 



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